Authorities in Idaho are searching for two children tied to a suspicious death case, while their mother and stepfather are wanted for questioning in connection with their disappearance.

Seven-year-old Joshua Vallow and 17-year-old Tylee Ryan have not been seen since September but their parents have not reported them missing, according to the Rexburg Police Department, who also said the children may be in danger. The search for the children began on Nov. 26 when extended family told police that they were not able to get in touch with Joshua, who has special needs. When the police contacted the children’s parents, Lori Vallow and Chad Daybell, they lied about Joshua’s whereabouts.

On Nov. 27, Rexburg police executed search warrants at locations associated with Vallow and found that the couple had vacated their home and left Rexburg entirely—they haven’t been seen or heard from since. Vallow and Daybell were married a couple of weeks after Daybell’s first wife, Tammy Daybell, was found dead on Oct. 19 in her home at age 49.

Authorities now believe that her death is suspicious and an autopsy will be conducted this month to determine the cause of her death, which was initially believed to be natural. Rexburg police are asking for anyone with information about the children to call their office at 208-359-3000.