Updated

At least 40 young men who drowned may have died by far more sinister means — serial killings at the hands of a national gang that revels in murdering young men and leaving smiley-face markings at the scene, a team of retired New York City police detectives and criminal justice investigators said Monday.

They believe the victims, including University of Minnesota student Chris Jenkins and Fordham University student Patrick McNeill, didn't accidentally drown but were actually killed by members of the so-called "Smiley Face Gang," according to KSTP-TV, which first reported the story.

A smiley-face symbol was found painted at some of the drowning locations — in Ohio, Pennsylvania, Indiana, Wisconsin and Iowa, the station said.

"They're telling you here that they're into evil, they're very happy as most serial killers are," retired NYPD Det. Kevin Gannon said at a press conference Monday. "They're content with their work and what they're doing and the fact that they're thwarting the police."

Click here to read more on this story from the KSTP.com.

Jenkins' body was discovered in the Mississippi River about four months after he disappeared in 2003. To police, his death looked like an accidental fall after a night of drinking.

McNeill drowned in New York City in 1997, also after bar-hopping.

The task force that formed to solve the crimes believes a national crime network has killed at least 40 men — mostly white college students and 20-somethings, often with high grades and impressive athletic records — in about 10 different states.

The team investigated 89 separate cases dating back a decade and said it had connected 40 of them through a variety of evidence — including matching sets of gang graffiti.

It was Jenkins' death, however, that tipped off police. His body was found encased in ice in the Mississippi, his hands folded across his chest in an odd pose that was inconsistent with a chance drowning.

Gannon and another NYPD detective, Anthony Duarte — along with the other investigators — believe a gang of killers has been trolling interstates from New York to Wisconsin, staging the drownings.

The FBI and local authorities don't necessarily agree with the theory that all the drownings are linked and the work of a gang.

But families of the victims have long believed their loved ones' deaths were suspicious.

"The people that murdered Chris have murdered before him and they've also murdered people after him, Jan Jenkins told KSTP. "Those people are still at large."

FOX News' Eric Shawn contributed to this report.

Click here for more on this story at MyFOXNY.com.