Seoul, South Korea(CNN) South Korea is searching for answers after Halloween celebrations in the capital Seoul turned into one of the country's worst disasters, with authorities declaring a national mourning period as they investigate how a chaotic crush left at least 151 people dead.
Tens of thousands of costumed partygoers -- mostly teenagers and young adults -- had poured into the popular nightlife neighborhood Itaewon to enjoy South Korea's first Halloween celebration since it lifted Covid restrictions such as crowd limits and face mask rules.
But the festivities descended into chaos, with photos and videos on social media showing huge crowds crammed into a narrow alley. Eyewitnesses described partygoers being packed so tightly together it was difficult to move around or even breathe.
Suah Cho, 23, described walking through an alley when "suddenly, some people started pushing each other, and people were screaming." The screaming went on for 15 minutes, she said, adding: "It was just panic."
"Some people were going forward and some people were going backward, and then just they were pushing each other," she added. She was able to escape into a building along the alley, where she watched the disaster unfold. She said some people had told her that "people were climbing the building to survive."
Authorities are still investigating what caused the incident, but Choi Seong-bum, chief of the Yongsan-gu Fire Department, said it was a "presumed stampede" and that many people fell, injuring at least 82.
The dead included at least 19 foreign nationals, including people from Iran, Norway, China and Uzbekistan, he said. One Thai national is among the dead, the Thai Foreign Ministry said.
The chaos of Saturday turned into shock and grief across the country on Sunday. Many victims' families have gathered at a nearby center in Itaewon, where officials are compiling the names of the dead and missing as they race to identify bodies.
So far, more than 90% of those killed have been identified, said Minister of Interior and Safety Lee Sang-min in a briefing on Sunday. He added that about 10 people can't be identified because some are under the age of 17 -- too young to carry a national ID card -- and others are foreigners.
But many remain missing, with families left anxiously calling hospitals and visiting morgues. By 2 p.m. local time on Sunday, Seoul authorities had received more than 3,580 missing persons reports, said the city government.
One mother, Ahn Yeon-seon, told South Korean news agency Yonhap her 19-year-old daughter had gone out to celebrate with her boyfriend for one of their last dates before he left for mandatory military service.
Several hours after the couple left, her daughter's boyfriend called crying, saying she had been "under a pile of people for over an hour and that he'd tried to pull her out but couldn't," Ahn said, according to Yonhap.
Since then, Ahn has been searching hospitals for her daughter, waiting for confirmation of what happened to her. "I'll just keep searching," she told Yonhap.
And, though the government has launched an investigation and promised new measures to prevent similar incidents from happening again, questions are emerging about how such a disaster could have occurred at all.
Cho, the 23-year-old who escaped the crush, said she saw no police or officials trying to control the crowd before the crush began. Even after they arrived later in the night, the sense of confusion and panic continued.
"The police officer was screaming, but we couldn't really tell that was a real police officer because so many people were wearing costumes," she said. "People were literally saying, 'Are you a real police officer?'"
Authorities received the first emergency calls of people being "buried" in crowds at 10:24 p.m. in Seoul (9:24 a.m. ET). As the news broke, Yonhap reported that some people had suffered from "cardiac arrest," with others reporting "difficulty breathing."
However, officials said there were no gas leaks or fires on site.
Lee Sang-min, Seoul's interior and safety minister, said on Sunday that "a considerable number of police and security forces" had been deployed to another part of Seoul on Saturday to deal with protests there.
Meanwhile in Itaewon, the crowd had not been unusually large, he said, so only a "normal" level of security forces had been deployed there.
But as the disaster unfolded, it prompted a massive response. More than 1,700 emergency response forces were dispatched on Saturday night, including 517 firefighters, 1,100 police officials, and about 70 government workers.
Social media videos showed police had taped off an area where people were performing compressions on other partygoers lying on the ground as they waited for medical help. Others showed people dressed in Halloween costumes lying on the street and on stretchers as first responders rendered aid and ambulances lined up to take away the injured.
South Korean President Yoon Suk Yeol convened an emergency meeting in the early hours of Sunday, and later visited the scene to receive briefings from emergency officials.
Addressing the nation, he called a national period of mourning "until the handling of the accident is concluded." Prime Minister Han Duck-soo later said the period of mourning would end at midnight of November 5.
"A tragedy that should not have happened occurred in the middle of Seoul last night on Halloween," Yoon said. "I pray for those who died in an unexpected accident and hope that the injured will recover quickly."
He also said the disaster would be investigated, with measures put into place to ensure similar incidents never happen again.
"We will have relevant ministries such as the Ministry of the Interior and Safety conduct emergency inspections not only for Halloween events but also for local festivals and thoroughly manage them so they are conducted in an orderly and safe manner," Yoon said, adding that a "multi-purpose emergency system" would support both the injured and the families of the dead.
Also on Sunday, Prime Minister Han Duck-soo said the government would provide a fund for families of the deceased and injured. It will operate "a funeral support team and respond fully to the treatment of the injured," and provide psychological treatment for those affected, he said.
The government will also "actively consult with diplomatic offices to ensure there is no shortage of support," Han said.
"Our country has a history of overcoming disasters with all citizens united in one mind," he said, adding: "I earnestly ask all the people to join so that we can overcome sorrow and rise again."
The government has declared the district of Yongsan-gu, where Itaewon is located, a special disaster area.
The Seoul Metropolitan Government said it would set up a joint memorial altar at Seoul Plaza Monday morning, with another joint memorial altar in Itaewon.
People fly into Seoul from all over Asia to celebrate Halloween in Itaewon, and this year's event was seen as a welcome return of festivities after the pandemic. Hotels and ticketed events in the neighborhood had been booked solid ahead and large crowds were expected.
One eyewitness, Sung Sehyun, said the space was like a "jammed subway," and that he had to push his way through the throng earlier in the night to get clear of the busy streets.
"I was lucky to get through (but an) hour later, I heard people got killed. Because people got stamped on ... and people got jammed together," he said
Juliette Kayyem, a disaster management expert and national security analyst for CNN, said the city's density -- and how common crowds are in Seoul -- may have played a role in the tragedy.
"People in Seoul are used to being in packed spaces, it's possible they might not have been fully alarmed by the packed streets," she said. "Panic is always a factor, and there is a danger of being too used to being in crowded spaces."
It's hard to pinpoint what might have triggered the crush -- but authorities "would have anticipated high numbers ... before Saturday night," she added. "There is a responsibility on the part of the authorities to be monitoring crowd volume in real time, so they can sense the need to get people out."
Around the world, leaders sent their condolences to South Korea and those affected by the disaster.
"Jill and I send our deepest condolences to the families who lost loved ones in Seoul," US President Joe Biden wrote in a statement. "We grieve with the people of the Republic of Korea and send our best wishes for a quick recovery to all those who were injured."
The United States government is ready to provide South Korea with "any support it needs," White House National Security Adviser Jake Sullivan wrote on Twitter Saturday. One US citizen was injured in the crush, authorities said.
British Prime Minister Rishi Sunak tweeted: "All our thoughts are with those currently responding and all South Koreans at this very distressing time." In tweet written in French and Korean, President Emmanuel Macron said "France is by your side."
Itaewon, once shunned by locals as a seedy, red light district, has transformed into one of Seoul's top party venues. Known for its nightlife and trendy restaurants, the neighborhood comes to life at night.
It is also home to Seoul's thriving Muslim and gay communities, and is located near a US army base.