Agents investigated the area around this white vehicle found near the blast.

Law enforcement responded in full force to a powerful explosion near Road 34 off Highway 26 Thursday morning and closed the main route from Portland to Mount Hood for the entire day to investigate the scene.

Clackamas County Sheriffs were assisted by agents by Alcohol, Tobacco and Firearms and the Federal Bureau of Investigation. The FBI reported that the blast was caused by material that target shooters use to make exploding targets. The explosion left a 10-foot-wide crater in the Mt. Hood National Forest, just off U.S. 26 in the woods.

The man who caused the explosion and died from it has been identified as Jeffrey Rodger Williams, and the cause of death has been determined a suicide.

Mileposts 45-53 of U.S. 26 were closed in both directions from about 7 am until about 9 pm as bomb squads and agents combed the area for clues. Bomb technicians used a robot to investigate a white vehicle found near milepost 48. The robot opened the car's trunk and removed a backpack.

The white car was registered to a resident at a Northeast Portland apartment complex. Police officers searched the apartment complex on NE Halsey Thursday afternoon, reportedly finding no explosives. The incident appeared to be isolated.

The highway was re-opened at about 9 pm Thursday.

In addition to the FBI and ATF, the explosion also brought responses from the Forest Service, the Oregon State Police, Portland Police Bureau, West Linn, Gresham and Vancouver Police, Hoodland Fire District, American Medical Response and the Oregon Department of Transportation.