SPRINGVILLE, Utah — Police say a preliminary autopsy has ruled out any violent assault in the deaths of five Utah family members, including three children.

There was no evidence of stabbing or gunshot wounds or other visible injuries to the five found dead Saturday night in their home in Springville, investigators said.

The five were identified as Benjamin Strack, 37, his wife, Kristi, 36, and three of their children, Benson, 14, Emery, 12, and Zion, 11.

Police Lt. Dave Caron said the cause of death has not been determined, and will not be until an analysis of blood samples.

While a test of air in the house by firefighters did not find any carbon monoxide, investigators have not ruled that out.

The front door of the house was open and the back door was cracked open before firefighters arrived, Caron said, and the gas could have ventilated before the test.

“We haven’t ruled out anything except there was no violent trauma. We’re going to look at everything,” Caron said.

The bodies were found shortly before 8 p.m. in the parents’ bedroom by an older son, who went to the duplex after he did not hear from the family as expected.