The father of two children missing from a home where three people were killed failed parts of a lie detector test, but is not a suspect in the case, authorities said.

Steve Groene (search) said in a television interview that he lacked an alibi and failed portions of a voluntary polygraph test administered by the FBI (search), but Kootenai County sheriff's Capt. Ben Wolfinger said that was not enough to make Groene a suspect.

"There is no evidence linking Steve Groene to this crime, to make him a suspect or a person of intere distraught and upset."

Brenda Kay Groene, 40, her son, Slade, 13, and her boyfriend, Mark Edward McKenzie, 37, were found bound and beaten to death May 16 at their home outside Coeur d'Alene. There were no signs of forced entry. Initial toxicology reports showed the two adults had used illicit drugs.

Officers believe the two younger children, who are still missing, were inside the home when the killings occurred, Wolfinger said.

The FBI posted a $100,000 reward Monday for information about the children, in addition to a local reward of about $7,500, said FBI agent Tim Fuhrman.

In an interview Sunday with FOX News Channel's "At Large with Geraldo Rivera," (search) Groene said the FBI believed he was lying when he said he did not know where the children are.

Groene also said no one could vouch for his alibi. He said he was home watching TV, talking on the phone and sleeping at the time. The woman he lives with, his former mother-in-law, was asleep and could not vouch for his whereabouts, Groene said.

Groene also acknowledged he and his ex-wife argued on May 13. He said he wanted the children to stay with him the following night and she refused, saying he needed to give more advance notice when he wanted to see the children.

"I wouldn't call it a fight. It was our normal argument over me not giving them — they always called it not fair warning, that I didn't call ahead enough," he said.

Groene said he volunteered to take a polygraph and undergo DNA and urine tests.