Idaho police and FBI agents investigating two missing children swarmed a home owned by their stepfather and his mysteriously deceased first wife.

Fremont County Sheriff Len Humphries told East Idaho News that investigators developed probable cause for a search warrant of the Salem house. Officers with rakes and metal detectors could be seen scouring the snow-covered backyard.

“This has been in the works for several days,” Humphries told the news site. “When you are doing an investigation, you have to accumulate evidence, and the process takes time.”

The home is where Tammy Daybell was found dead on Oct. 19. Her husband, doomsday writer Chad Daybell, soon married Lori Vallow, whose own husband had died just a few months earlier.

The newlyweds attracted the attention of law-enforcement when Vallow’s extended family reported they had not heard from her two children, 17-year-old Tylee Ryan and adopted 7-year-old Joshua “J.J.” Vallow.

According to authorities, the couple said the kids were with family in Arizona, a claim which turned out to be a lie. Then Daybell and his new bride fled the state, police said.

The search for the children soon expanded to include other mysteries.

Tammy Daybell’s body was exhumed so investigators could conduct the autopsy that her husband had rejected when she died of supposedly natural causes.

Officials are also looking into the death of Charles Vallow, Lori’s first husband, who was reported shot to death by her brother, Alex Cox, on July 11. Cox died of unspecified causes on Dec. 12, leaving Tylee and J.J. the only other witnesses to Charles’ death.

Also under scrutiny is Chad and Lori’s interest in doomsday scenarios and near-death experiences. Both were contributors to a website called Preparing a People that says its goal is to “help prepare the people of this earth for the second coming of Jesus Christ.”

Vallow’s family members have said they believe the couple was in a cult, but Preparing a People’s owners have denied that and said it is a media company with no religious affiliation.

Police earlier this week put out an appeal to Daybell and Vallow to come forward and reveal the whereabouts of the children.

“It is astonishing that rather than work with law enforcement to help us locate her own children, Lori Vallow has chosen instead to leave the state with her new husband,” they said in a statement.

A week earlier, a local lawyer retained by the couple had put out a statement denying any wrongdoing.

“Chad Daybell was a loving husband and has the support of his children in this matter. Lori (Vallow) Daybell is a devoted mother and resents assertions to the contrary. We look forward to addressing the allegations once they have moved beyond speculation and rumor,” lawyer Sean Bartholick said.

Bartholick said this week he had no further comment.