SAN DIEGO -- A registered sex offender arrested on suspicion of killing a missing 24-year-old Santee woman said in a jailhouse interview that he doesn't know the woman and didn't kill anyone.

Robert Steven Carson of Spring Valley told 10News Saturday during an interview that he doesn't know Brittany Hart, who disappeared 17 days ago.

"I didn't kill anybody," he said.

Carson also expressed sympathy to Hart's family during the interview.

Hart's body has not been found, though friends, family and strangers --led by private investigator Bill Garcia -- searched the Sweetwater Reservoir area near La Presa this weekend.

There have been some false alarms during the search, including the discovery Sunday of some possible human remains following reports of a foul odor in the search area.

Garcia said he found some grocery bags that turned out to contain remains that were not human, which he said was verified by the Medical Examiner's office.

Garcia revealed some new information today about Hart's missing 1998 charcoal gray Ford Ranger with California license plate 6M91555.

He said the pickup truck was previously painted red, and there are still red splotches in the truck bed and inside the gas cap.

Carson pleaded not guilty to a charge of murder Friday and is being held without bail, pending trial.

Hart's sister, Brandy Reynolds, said she was "appalled" that a repeat offender such as Carson, 40, had been allowed back into society.

"People like him should not be able to walk free," she said. "I don't think I've ever hated anybody in my life. I hate him."

Reynolds said her family still clings to the hope that Hart is alive.

"The biggest focus right now is finding her truck ... (and) finding her," Reynolds said.

Carson was arrested at his Marie Street home Tuesday night. Detectives with a search warrant found blood in the basement, prosecutor John Rice told Superior Court Judge Patricia Cookson during the suspect's arraignment.

Cellular telephone records indicate that the day before Hart vanished, she and Carson had contact, the prosecutor said.

Carson has five felony convictions, including one from 1986 for assault with intent to rape three women. Carson also has a case pending in the South Bay for allegedly trying to evade officers in Coronado.

Carson was convicted in 2003 of misdemeanor sexual battery.

Anyone with more information about Hart or her truck was urged to call San Diego County Crime Stoppers at 888-580-TIPS. Callers can remain anonymous.