Police are searching Yellowstone National Park in the hunt for "doomsday cult" mom's missing children, investigators revealed.
The investigators are searching for missing Idaho teen Tylee Ryan, 17, and her younger brother, seven-year-old Joshua "JJ" Vallow. The children have not been seen since September.
Their mother, Lori Vallow, was arrested in Hawaii on child abandonment and desertion charges after she failed to comply with a Madison County, Idaho, order to physically produce her children by 30 January.
Relatives say a radical doomsday group, which Ms Vallow is believed to be in, could be the cause of the children's disappearance.
Ms Vallow reportedly believes she is "a god assigned to carry out the work of the 144,000 at Christ's second coming in July 2020".
The children went missing while the family was living in Idaho, according to reports.
JJ, who has autism, was adopted by Ms Vallow and last seen alive on 23 September at his Kennedy Elementary School in Rexburg, Idaho, according to an affidavit obtained by ABC News.
Ms Vallow then called the school the following day to inform administrators JJ would no longer be attending. Instead, she said she would be homeschooling the child.
Doorbell footage obtained by investigators also shows JJ in the family's Idaho neighborhood playing outside in September.
Police are looking into Yellowstone National Park because phone records show Tylee, her younger brother, their mother, and uncle all visited the park on 8 September, CBS News reports.
A photo "obtained from Ms Vallow's iCloud account" shows Tylee at the park. There is no sign of life since for the teen.
In order to search the park, though, investigators have to wait until the snow melts.
An investigation into the missing children started after a welfare check by police in November. Ms Vallow is accused of lying to investigators at the time about JJ being in Arizona with a friend, Fox News reports. She and her fifth husband, Chad Daybell, then fled to Hawaii amid questions about their children and their whereabouts.
Relatives are hopeful Ms Vallow's arrest will help investigators determine what happened to the two children. Ms Vallow is being held in jail on $5m bail.
