"I know he killed Stacy," said Peterson's stepbrother Thomas Morphey.
Area resident Michelle Williams spotted the blue barrel in the river earlier this week and notified police.
"A blue barrel in the river is something people would want to know about, especially police," Williams said. "When we first saw the blue barrel we first thought of Stacy Peterson."
Drew Peterson has denied any involvement in Savio's death and Stacy Peterson's disappearance, even as the majority of public opinion remains suspicious. Peterson has pleaded not guilty to first-degree murder charges in the death of Savio, whose body was found in her empty bathtub with a gash in the back of her head. He remains jailed on $20 million bond.
Investigators say the partial remains of a small woman clad only in underwear were found by a barge clean-up crew on the bank of the Des Plaines River near rural Channahon, Ill.
The Will County coroner's office said it will conduct an autopsy today and investigators say DNA will be crucial in identifying the body.
"If it isn't Stacy today," Peterson neighbor Sharon Bychowski said," we'll keep looking for her."
Peterson's Monday arraignment in the Savio case was cut short when prosecutors made a surprise request for a new judge to oversee the case.
His attorneys have vowed to get the $20 million bond reduced but must wait in the wake of the prosecution's request that Judge Richard Schoenstedt be removed from the case, citing suspected bias against the state.
A spokesman for the Will County State's Attorney's Office declined to elaborate on the request.
In November, Schoenstedt dismissed felony gun charges against Peterson after prosecutors refused to give defense attorneys internal documents that described communication between the Illinois State Police and prosecutors. Those documents reportedly led to the decision to arrest Peterson on the gun charges.
After Monday's hearing, Peterson's attorney, Joel Brodsky, criticized prosecutors.
"A motion by the state for a substitution of judges is almost unheard of, extremely rare. And I just think it indicates to us the weakness of the state's factual position," he said. "It shows that they don't want to deal with this case on the facts but want to try to get this case to a place where they're more comfortable, as opposed to having a judge ... who's gonna listen to both sides."
Savio's death was initially ruled a drowning accident but a second autopsy, conducted in 2007 after the disappearance of Peterson's fourth wife, ruled it a homicide. Peterson is also a suspect in the disappearance of his fourth wife, Stacy Peterson.
Peterson has made headlines not only for his legal troubles but for his jokes about it.
"Drew's personality is, I'll say ... unique," Brodsky said earlier today on "Good Morning America." "But he's honest."
If Peterson does take the stand in his defense, Brodsky said he thinks that honesty would only help him. But finding an impartial jury, he said, could be difficult.
Peterson has said he expects to be found innocent of Savio's murder and has maintained a seemingly cavalier attitude toward his May 7 arrest.
As he was being led into court, Peterson, handcuffed and wearing a red jumpsuit, joked with reporters, saying, "What about this bling? Look at this bling. Three squares a day in this spiffy outfit. How can you beat that? Look at this bling. My God."