BOISE, Idaho (AP) — Officials say an electrical fault in a light fixture caused a house fire that killed twin 3-year-old boys in the north-central Idaho town of Weippe.

The fire happened early Friday, and by the time firefighters arrived the home was fully engulfed and the flames were too intense for them to immediately enter the home.

The Idaho Department of Insurance released a prepared statement Tuesday saying that while smoke detectors were said to have been in the home, no alarms were heard or located during the investigation.

The mother of the children, Hannah Hueth, told investigators the twins, John and Shawn Carr, were sleeping in the living room when she went to bed around midnight. She woke up to smoke and alerted the father, Chance Carr, who tried to rescue the children but was driven back by heavy smoke and heat.

The Insurance Department statement said Carr then helped Hueth climb out the window, and she ran around to the front of the house to try to enter to reach the boys. She was unable to because of the intense smoke and flames, and stopped a passing motorist to call 911.

Idaho State Fire Marshal Knute Sandahl said the case was one of the most difficult he’s dealt with in 35 years on the job. The search for the children was hindered by a collapsed roof and fire-weakened floors, but after five hours of searching, responders found the twins in the kitchen area of the home.

“The tragic loss of these two boys impacted every state fire marshal investigator and first responder there and no doubt the entire community of Weippe,” Sandahl said. “Our hearts go out to the family of John and Shawn.”