Authorities rule out sighting
Massive search on for missing siblings
An Amber Alert was issued for siblings Shasta and Dylan Groene.
A sheriff's hot line has been established for any information about the case: 208 446-2292 or 208 446-2293.
Authorities hope home video of Shasta Groene will help find the girl and her brother.
Amber Alert issued for two children in wake of triple slaying.
COEUR D'ALENE, Idaho (CNN) -- Authorities have ruled out a purported sighting of two missing Idaho children at a Bonners Ferry, Idaho store, said a spokesman for the Kootenai County Sheriff's Department.
The town is about 70 miles north of their Coeur d'Alene house, where the bodies of the children's mother, Brenda Groene, 40; her boyfriend, Mark McKenzie, 37; and their 13-year-old brother Slade; were found Monday.
Authorities have since launched a massive search for 9-year-old Dylan and 8-year-old Shasta.
The van that was reported carrying the children turned out to be a false alarm, said Sheriff's spokesman Capt. Ben Wolfinger.
And the child thought to be Dylan had long, collar-length hair; Dylan has a crewcut.
The coroner's office concluded Thursday that the three victims died of blunt force trauma to the head.
They were bound, and the blows left a blood-splattered crime scene, said Wolfinger.
The coroner's office said Slade and his mother died of "lacerations and contusions of the brain due to skull fractures." McKenzie died of contusions, or bruises, to the brain.
The time of death could not be immediately determined. Authorities said the victims and two missing children were last seen alive Sunday night at a barbecue at the home. The bodies were discovered Monday after neighbors called police when they didn't see any activity at the home.
Wolfinger invited all those who attended the barbecue to contact authorities.
"We need to talk to these folks and we need to get their elimination prints, so we can figure out who was here legitimately and who may have been involved in this crime," Wolfinger said.
Steve Groene, the father of the two missing children, fought back tears Thursday as he urged those who might be holding his children to set them free.
"Please, please release my children safely. They had nothing to do with any of this," the father said. "Release them in a safe area where law enforcement can find them, call the help line, let them know where they can be found. Please, we need the safe return of those children."
Searchers were combing thick woods surrounding the house.
"We're looking for anything right now," Wolfinger said. "Our ultimate goal is to find the children."
In the Amber Alert issued for the missing children, authorities described Dylan as 4 feet tall, 60 pounds, with short blonde, crewcut hair and blue eyes; and Shasta as 3-foot-10, 40 pounds, with long auburn-brown hair and hazel green eyes.
CNN's Betty Anderson, Ninette Sosa and Alina Cho contributed to this report.