Investigators are using the cellphone records of an Indiana man already charged in the slayings of two women to pinpoint his movements after he told police he liked to check on the status of bodies he'd previously stashed after a fresh kill, authorities said.

Illinois law enforcement officials told The Associated Press Wednesday that Darren Vann, 43, may have traveled to Chicago's south suburbs between the time 19-year-old Afrikka Hardy's body was discovered Friday in Hammond, Indiana, and Saturday when Vann was arrested in nearby Gary. The officials spoke on the condition of anonymity because they weren't authorized to discuss the investigation.

Indiana police say Vann, a convicted sex offender, has confessed to killing Hardy and six women whose bodies were found over the weekend in abandoned houses in Gary. He has been charged with murder in the deaths of Hardy and 35-year-old Anith Jones, whose body was found Saturday in Gary.

A judge ordered Vann be held in contempt of court Wednesday when the former Marine refused to even acknowledge his name during an initial court hearing in Hardy's slaying.

Magistrate Judge Kathleen Sullivan asked Vann if he understood the reason for the hearing but he just stared back silently.

"Mr. Vann, are you choosing not to take part in this hearing?" Sullivan asked the shackled Vann, who was flanked by two Lake County Jail guards at the lockup in Crown Point.

Sullivan urged Vann's public defender, Matthew Fech, to tell his client "that he stays in jail the rest of his life until this hearing takes place." Fech urged Vann to speak, but he again offered no response. Sullivan found Vann in contempt and said she would schedule another initial hearing for next week.

Lake County Sheriff John Buncich said Vann's demeanor has otherwise been "quiet, calm and collected," but that his silence, if it persists, could raise complicated legal questions that would slow the prosecution process.

Sullivan also issued a gag order barring investigators from interviewing Vann unless they first get his permission through his attorney, Buncich said.

Vann was arrested and charged Saturday in the strangulation death of Hardy, whose body was found Friday in a bathtub at a Motel 6 in Hammond, 20 miles southeast of Chicago.

On Wednesday, he also was charged in the death of Jones.

Five more bodies were found Sunday in other homes, said Hammond Police Chief John Doughty, who identified two of the women as Gary residents Teaira Batey, 28, and Kristine Williams, 36. Police have not determined the identities of the other three, including two whose bodies were found on the same Gary block as Jones' body.

Investigators were searching 16 abandoned buildings in Illinois on Wednesday and Thursday as part of the investigation into Vann's movements after Hardy's body was found, authorities said. Police say Vann has hinted that his crimes stretch back 20 years.

Buncich said worried family members "from all over the Midwest" have asked whether their relatives are among Vann's victims.

Vann was convicted in 2009 of raping a woman in Austin, Texas. He was released from prison last year and moved back to Indiana. Before that conviction, he served a year in prison in Indiana after he grabbed a Gary woman in a chokehold in 2004, doused her with gasoline and threatened to set her on fire.

In both cases, the charges against Vann were reduced in plea bargains, and Texas officials deemed him a low risk for violence. Vann registered as a sex offender in Indiana and police checked in September that he lived at the address he provided.