Investigators searched the home of a suburban Chicago police sergeant for the second time Tuesday night whose wife disappeared last week.

Stacy Peterson, 23, was reported missing Oct. 29 after she didn't arrive to a friend's house. Peterson is married to Bolingbrook, Ill., police Sgt. Drew Peterson, 53.

The family of Stacy Peterson believes she is dead, vowing to search for her until she is found.

"I've got to keep strong and keep going. I'm not going to stop until I find her," said Cassandra Cales, Stacy Peterson's sister.

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Illinois State Police searched the Peterson home last week. Authorities seized two vehicles, computers, cell phones and other items.

Will County state's attorney's office spokesman Charles Pelkie said he couldn't offer any details about the warrant for Drew and Stacy Peterson's Bolingbrook home.

Prosecutors want to interview their children for any possible clues that could help in the investigation.

Texas EquuSearch, a nonprofit group that helps search for missing persons, combed several areas near the home with divers, helicopters, horses and dog teams.

"It doesn't look good," Tim Miller, founder of Texas EquuSearch, said. "If something has happened to her, we know that every day that she's out there more and more evidence is gone and it's harder to determine cause of death."

Drew Peterson, 53, a sergeant in the Bolingbrook Police Department, has said his wife phoned him and told him she had left voluntarily for another man. But Stacy Peterson's family has said she feared her husband, was making plans to divorce him and would not have willingly left her children.

Authorities also reopened an investigation into the death of Drew Peterson's third wife, Kathleen Savio, who in 2004 was found dead in a bathtub at the age of 40. A coroner ruled the death accidental.

The Associated Press contributed to this report.