Investigators cleared a man they called a "person of interest" in the bloody murders of three people and the disappearance of two children after the man passed a lie detector test.

Also Thursday, the Kootenai County Coroner's Office revealed the cause of death in the murders: blunt impact trauma to the head. The coroner's office released its preliminary findings in a press release after conducting autopsies of the victims.

Police determined that the person of interest, Robert Roy Lutner (search), was not involved with the crimes after seven hours of questioning, sheriff's Capt. Ben Wolfinger said Thursday afternoon.

"He had nothing to do with the death scene or the abduction of the children," Wolfinger said, referring to 8-year-old Shasta Kay Groene (search) and 9-year-old Dylan James Groene (search).

Wolfinger said Lutner was at the kids' home on Sunday night, the night before the bodies of their brother, mother and a man were found. Lutner told authorities there was a "barbecue-type get-together" at the house and Wolfinger asked for anyone who may have been there to call authorities.

"We'll look at anything," Wolfinger said. "We're not ruling anything out except Mr. Lutner at this point."

Lutner contacted authorities after learning he was being sought and voluntarily agreed to take a lie detector test, Wolfinger said, adding that Lutner was on probation for an unemployment fraud conviction and delayed turning himself in because he was worried about violating the terms of his probation.

Police wanted to talk with Lutner, 33, of Hayden, to determine whether he may have seen something, or met someone at the home east of Coeur d'Alene where the bodies were found.

Shasta Groene, 8, is 3-feet-10 and 40 pounds with long auburn hair and hazel eyes, and her 9-year-old brother, Dylan, is 4 feet and 60 pounds with a blond crew cut and blue eyes.

The bodies of their mother, Brenda Kay Groene, 40, and brother, Slade Vincent Groene, 13, and Mark E. McKenzie, 37, of Coeur d'Alene, were found in the house.

Asked if the children might still be alive, Wolfinger said: "all you can do at this point is hope."

At a separate late afternoon press conference, the father of the two children made a short, emotional appeal.

"Please, please release my children safely," Steven Groene said as he was surrounded by family members. "They had nothing to do with any of this."

To help with that return, Wolfinger said $70,000 had been pledged so far for a reward fund but that officials were still working out the details of how the reward would be offered.

Police released few details about the evidence found inside the house, but Wolfinger said there was "lots of blood."

"We know this was a triple homicide because all three victims were bound," Wolfinger said, declining to elaborate.

Authorities prepared to drain small ponds near the home. Wolfinger said officials would search "for evidence of any sort, or, God forbid, the children, but maybe a tool or weapon, anything."

The search also expanded from the siblings' home to nearby fields and woods where they are known to play. "The children are our number one priority," Wolfinger said.

Jesse Groene, 18, an older brother of the missing children, said his mother had been acquainted with Lutner for about two years. Jesse Groene is currently jailed for investigation of assault, battery, burglary and possession of stolen property.

Groene told The Spokesman-Review that his mother and McKenzie began dating about six years ago after she separated from Steven Groene, the father of her five children.

Jesse Groene also described McKenzie, who owned the house, as "my stepfather" and said he was the main source of income for the family.

The Associated Press contributed to this report.