(CNN) A vehicle packed with undocumented immigrants flipped Sunday, ejecting 12 people and killing at least five after a chase in south Texas, Dimmit County Sheriff Marion Boyd said.
Four people were killed at the scene about 50 miles from the Mexico border and a fifth person died at a hospital in San Antonio, the sheriff said.
The incident started after a Border Patrol agent in Carrizo Springs suspected smuggling when he saw a trio of vehicles pass him on a rural highway around 11 a.m., US Customs and Border Protection said. The agent stopped one vehicle and radioed a description of the other vehicles to other agents, the agency said.
A second agent stopped the second vehicle and several people were arrested from those two vehicles, but the third vehicle didn't stop when an agent tried to pull it over, Customs and Border Protection said.
A Dimmitt County Sheriff's deputy took over the chase just west of Big Wells, but the vehicle, which was traveling around 100 mph, lost control, ran off the roadway before flipping several times, landing on the highway, according to Boyd.
"We've seen this many, many times, in not only this county but other counties along the border," Boyd said. "It's a problem. ... This is, I think, a perfect example of why our borders need to be secure."
Boyd said there were 14 people in the vehicle that flipped. Authorities believe the driver and one passenger are US citizens.
Local law enforcement officers were familiar with the driver, who was in the area last week to either pick up undocumented immigrants or to scout, the sheriff said.
The other 12 passengers were undocumented immigrants, Boyd said.
Boyd said the victims were taken to hospitals. Six patients were taken to San Antonio Military Medical Center in San Antonio, Lt. Edwin Roberts said. He would not confirm if any of the patients had died.
The sheriff said he didn't know where the immigrants were from but said most migrants who travel through the area are from Central America or Mexico.
He said his deputies are often involved in chases pursuing people suspected of smuggling undocumented immigrants and drugs.
"I think we need a wall, in my opinion," he said, voicing support for President Donald Trump's proposal to construct a border wall with Mexico.
Boyd added: "If it can be built, I think it needs to be built. But along with that, there needs to be cameras. There needs to be sensors."
Footage from a motorist who witnessed the crash and posted video to Facebook shortly after shows at least four bodies on the highway, the mangled Chevrolet and several Border Patrol vehicles at the scene.
Yolanda Choates, a US Customs and Border Protection spokeswoman, directed questions to the sheriff's office.
When asked why Border Patrol agents started the chase, Boyd said, "It's called good police work."