Authorities reopened an investigation this week into the death of a Chicago suburb police sergeant's third wife after his fourth wife disappeared.

Stacy Ann Peterson, 23, was reported missing Sunday after she didn't arrive to a friend's house. Peterson is married to Bolingbrook police Sgt. Drew Peterson, 53, who is cooperating with police and is not considered a suspect.

"At this time there is no indication of any type of foul play or anything suspicious," said Lt. Ken Teppel, a spokesman for Bolingbrook Police Department.

State police are following up on leads, reviewing voicemails, text messages, e-mails and talking to family and friends in attempts to find the missing woman.

Drew Peterson told reporters Wednesday that he believes his wife is alive and said he is being treated unfairly in this case. Peterson urged the media to focus on looking for his wife and not on his past.

"Our interest right now is Stacy and finding Stacy," said Trooper Mark Dorencz.

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In 2004, Drew Peterson's third wife, Kathleen Savio, 40, was found dead in a bathtub, and a coroner ruled the death accidental. Prosecutors are reviewing the case.

Documents show that Savio filed for an emergency order of protection from her husband, writing in the file that "he wants me dead and if he has to he will burn the house down just to shut me up."

Stacy Peterson's family reported her missing early Monday, asking the state police to investigate.

Betty Morphey, Drew Peterson's mother, told FOX News that she just saw Stacy last weekend, talking about plans for Thanksgiving.

Morphey said she doesn't know anything about her disappearance, adding that Drew and Stacy were happy.

"As far as we know, everything is fine with them. They get along," Morphey said.

But Stacy Peterson is the third wife to vanish in the last six months in the Chicago area, the latest in a series of mothers whose families say they would never leave their children behind.

Chicago police found a body believed to be that of missing 39-year-old Alma Mendez, a mother of three, who disappeared Sunday on a jog near a forest preserve.

Mendez was last heard from on Sunday at about 2 p.m. when she left a friend a voicemail saying she had something important to talk about.

Meanwhile, on Tuesday, the family of Lisa Stebic, a Plainsville, Ill,. mother of two who disappeared six months ago, held a candlelight vigil in her honor. Stebic's estranged husband, Craig, and two children were not there.

The family of Lisa claims Craig Stebic cut all communication between Lisa's sisters and the children.

"Their last connection to their sister has now been severed," said Melanie Greenberg, cousin of Lisa Stebic.

Police named Craig Stebic a person of interest in the disappearance of his wife in July.

FOX's WFLD Chicago and The Associated Press contributed to this report.