Updated

Illinois State police have identified the person they think may have helped former police sergeant Drew Peterson move a large blue barrel from his bedroom to his vehicle the day after his 23-year-old wife was reported missing.

A law enforcement source tells WFLD FOX Chicago that the man who helped load a barrel into Peterson's SUV tried to commit suicide the next day.

Stacy Peterson, a mother of two and Peterson's fourth wife, was reported missing Oct. 29 by her family after she failed to show up to a friend's house. Drew Peterson is a suspect in her disappearance.

Click here to watch the video report from myFOXChicago.com.

• Click here for photos of Drew Peterson.

• Click here for photos of Stacy Peterson.

Volunteers searching for any signs of Stacy are looking for the barrel. Neighbors say Peterson had a blue barrel in his backyard.

Peterson's neighbor told police last week that he saw Peterson and the man load a barrel "big enough to put someone in" into the former police officer's SUV, according to a Chicago Sun-Times report.

On Monday, 64 special agents with the FBI joined the search for Stacy to help state authorities in their investigation.

"I'm not saying that we're going to be able to solve the case," said FBI agent Ross Rice. "I'm certainly not going to predict if or when it will ever be solved but having additional resources certainly can't hurt."

Meanwhile, Will County prosecutors reopened the investigation into the death of Peterson's third ex-wife, Kathleen Savio. Savio, 40, died in a bathtub in March 2004. Prosecutors say the death appeared to be staged to conceal a homicide and recently exhumed her body for a second autopsy.

Illinois State Police told FOX News on Sunday that "new information" prompted its appeal for more information about possible sightings of the cars that belong to Stacy Peterson or her husband, Drew, around the time that the woman vanished.

Investigators are asking anyone who may have seen the vehicles on Oct. 28 or 29 — the time of the 23-year-old Bolingbrook mother's disappearance — to come forward.

Police have released photos of the vehicles: A dark Blue 2005 GMC Yukon Denali belonging to Drew and the second a purple 2002 Pontiac Grand Am, belonging to Stacy, and asked the public to call its tipline at 815-740-0678 or "America's Most Wanted" at 800-274-6388.

Both vehicles were impounded by police on Nov. 1, and are still in police possession because of search warrant seizures.