(CNN) For investigators working on the cases of people whose remains were found on the shore of Lake Mead, time is the enemy.
The bodies -- one of which was found in a corroding barrel with a gunshot wound -- could have been submerged in the lake's depths decades ago, leaving the three sets of remains in advanced stages of decomposition and making it increasingly difficult to extract DNA. But officials have already discovered key details, which they revealed to CNN, including confirmation that the gunshot victim's death was a homicide.
When police arrived at the lake's Hemenway Harbor on May 1 to investigate the discovery of a set of remains in a barrel, investigators immediately treated it as a homicide investigation, not waiting to get a confirmation from the coroner, Lt. Jason Johansson of the Las Vegas Metropolitan Police homicide unit told CNN. The gunshot wound was obvious, he said, and the circumstances clearly suspicious.
Clark County Coroner Melanie Rouse has since preliminarily ruled the cause and manner of death was homicide by gunshot and also said her office is submitting specimens from the remains to try to extract DNA. If DNA is found, it will also be sent to the FBI, which is assisting in the case, she said.
The remains, dubbed Hemenway Harbor Doe by the coroner's office, are one of at least three sets uncovered due to the dramatically receding water levels at Lake Mead, which has plunged to unprecedented lows amid a critical water crisis in the West.
Police previously announced they placed the Hemenway Harbor Doe's approximate time of death as sometime in the mid-'70s to early '80s, based on the victim's clothes and shoes. Johansson told CNN that the clothing was so well preserved in the freshwater environment that investigators were still able to read the clothing labels.
But without an ID, investigators are extremely limited. And the more time passes, the harder it will be to identify aging witnesses and potential suspects.
"If you think about what the age of who your witnesses or anybody related to this case would be, many of them are getting older every day. And they're at an age where you have to worry, are they even alive? And so I would say that's probably our biggest concern right now," Johansson said.
Rouse has preliminarily determined that the age of the person in the second set of remains -- found on May 7 at Calville Bay -- is approximately between 23 and 37 years old. While she couldn't confidently determine how the person died -- meaning the preliminary cause of death is undetermined -- the coroner's office is sending specimens to be examined for any potential DNA.
The Calville Bay remains are more skeletal than the other two sets, Rouse said, which both still have organ tissue available for examination, despite being immersed in the lake. The cooler underwater temperatures would cause a body to decompose more slowly than if it were baking under the desert sun, she explained.
The final remains were found at the lake's Swim Beach on July 25 and the examination is still at an early stage, Rouse said. Unlike the other two, these are only partial remains and Rouse is still processing them to determine what can even be examined based on their condition, she said.
The remains are undergoing toxicology and other testing before a cause and manner of death can be determined, the coroner said.
Police are not investigating the other two sets of remains because there is so far no sign of foul play or suspicious circumstances in the deaths, Johansson said, but he has no doubt the circumstances of the Hemenway Harbor Doe's death are nefarious.
"Anytime you have a body in a barrel, clearly there was somebody else involved," he said.
Theories of mob involvement in the Hemenway Harbor Doe's death began to swirl as soon as details emerged that the remains were found inside a barrel. Those ideas were fueled even more when police announced the victim was likely killed at a time when organized crime had a strong grasp on Las Vegas.
But those ideas are "mere speculation" at this point in the investigation, Johansson said, denying that there is any solid evidence to support mob theories.
"Yes, Vegas does have a history in the past where we had a connection to violent crime, to organized crime back in the '60s, the 70s," he said. "However, right now, there's nothing in this investigation that is directly tying it organized crime."
At its height in 1983, Lake Mead was 1,225 feet above sea level. But as the climate crisis fuels a prolonged mega-drought in the West, the lake, which serves as the nation's largest reservoir, has plummeted to sobering levels. This year it hit its lowest level since it was filled in the 1930s.
One possible scenario for the second two remains is that they belong to people who previously drowned at the lake when water levels were high, a National Parks Service spokesperson told CNN. Recovery divers are limited on how deep they can go, so some drowning victims' remains do not get recovered, they said.
"The lake has drained dramatically over the last 15 years," Las Vegas Metropolitan Police Homicide Lt. Ray Spencer said in May. "It's likely that we will find additional bodies that have been dumped in Lake Mead" as the water level drops further.
The dropping water level has exposed a WW II-era landing craft, wrecked boats and the lake's original 1971 water intake valve, and officials expect more surprises may be in store.
In addition to traditional autopsies, examiners at the Clark County coroner's office have a number of techniques they can use to uncover details about a body, including X-rays, fingerprinting, forensic dentistry and analysis by forensic anthropologists, Rouse said.
"In cases where we are limited [on identification methods], we would also conduct DNA analysis," she said, noting that method may not be ideal for some extremely decomposed remains.
For the two sets of Lake Mead remains from which the office is trying to extract DNA, those specimens would have to be sent to a lab, she said.
The condition of the body is essential in the examination process, she said, because more degraded remains may not be able to be fingerprinted or provide dental information. The coroner's office was able to perform forensic dentistry on the first two sets of Lake Mead remains, she said.
Examiners then compare the dental information to a dental records database, she said, so it's especially important to investigators that a person's dental records were submitted to the database. Otherwise, there will be no match.
The coroner's office is sharing its findings with law enforcement, she said, including the FBI in the case of the homicide victim.
The FBI reached out to Las Vegas police to offer help in the investigation because the body was found on National Park Service land, Johansson said. The agency, which had a lively presence in the area during the mob's heyday, also offered the assistance of its Organized Crime Task Force if local police need it, he said.