The two injured men, ages 59 and 60, sustained what an Ontario Police Department news release described as "life-threatening and disfiguring injuries" when a homemade bomb went off Sunday.
Police believe the explosion occurred in the Bully Creek area west of Vale, Ore. They did not release the names of the injured men. Police Chief Mark Alexander said it's unclear whether the blast was an accident or a deliberate attack.
"That's what we've got to find out," Alexander said.
Officers obtained a search warrant and searched the home - with the help of the Nampa Bomb Squad - of the two injured men. They found materials and instructions for making bombs, Alexander said. It's unclear whether the two men are involved in violent activity or had plans for an attack, he said.
The bomb squad is now helping the Malheur County Sheriff's Office in examining the scene where the explosion occurred.
According to the release, police received a report that another person - also unidentified - who took the two injured people to St. Alphonsus Medical Center in Ontario may have another bomb in his vehicle. After the hospital closed off the parking lot around the vehicle and the Nampa Bomb Squad responded, that report was determined to be a false alarm.
One of the injured men has been transported by air ambulance to St. Alphonsus in Boise, and the other was transported to Oregon Health and Science University in Portland, Ore.
Besides the Malheur County Sheriff's Office and bomb squad, the Ontarios Police Department, U.S. Bureau of Alcohol, Tobacco and Firearms are investigating the incident.