Cops Clear 'Person Of Interest'

A man investigators had called a "person of interest" in the killings of three people was ruled out as a suspect Thursday, but police believe a party that was held at the family's home just before the murders may hold some clues into the whereabouts of the two missing children.

The man, Robert Roy Lutner, 33, of Hayden, voluntarily took and passed a polygraph test during a seven-hour interview with investigators, Kootenai County sheriff's Capt. Ben Wolfinger said. Lutner said he saw the three alive when he attended a "barbecue-type get-together" at their rural home Sunday night, less than 24 hours before the bodies were found.

"He had nothing to do with the death scene or the abduction of the children," Wolfinger said.

Lutner, a concrete worker with an extensive criminal record, contacted authorities through his probation officer Wednesday after learning he was being sought for questioning, Wolfinger said.

He was the last known visitor to the rural house where the victims, Brenda Kay Groene, 40; her 13-year-old son, Slade Vincent Groene; and her boyfriend, Mark McKenzie, 37, were discovered slain Monday evening.

Meanwhile, at a news conference Thursday, the missing children's father begged for information leading to their return.

"I'd like to address my children's abductors or abductor. Please, please release my children safely. They had nothing to do with this. Release them in a safe area where law enforcement can find them,'' said Steve Groene.

CBS's Teri Okita reports a forensics team went inside the Groene's home for a second day Thursday looking for more evidence. Wolfinger would not elaborate on what they found, only saying there was a lot of blood.

An Amber Alert had been issued Tuesday for Groene's missing children, Dylan Groene, 9, and Shasta, 8.

Wolfinger urged anyone else who attended the Sunday gathering to contact the sheriff's office. Otherwise, investigators searching the house for fingerprints might assume they are suspects, Wolfinger said.

Hundreds of tips have flowed in, but nothing solid, Wolfinger said.

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.

Wolfinger said investigators are hoping for a break in the case.

"I guess really the break we're looking for is somebody who see those children, see those children in a restaurant, a truck stop, at any place, anywhere in the nation right now and call our office or their local law enforcement agency," Wolfinger told CBS News Early Show co-anchor Harry Smith.

Police released few details about the evidence found inside the house. Investigators decided to keep secret how the three died so they can eliminate any false confessions that might come in.

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

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.

At Slad Groene's school, ten crisis counselors are helping students cope, reports CBS News Correspondent John Blackstone.

"There's fear out there, and the fact that this can happen in Coeur d'Alene is shocking," said school principal Chris Hammons.