Air Force officials say a brake valve failure caused an Ellsworth Air Force Base B1-B Lancer bomber to collide with two aircraft rescue firefighting vehicles last spring.

No one was injured in the March 8 accident at Andersen Air Force Base in Guam. The B-1 with the 28th Bomb Wing, and the two emergency response vehicles sustained $5.8 million in damages.

According to an Air Force news release, an Air Combat Command accident investigation board ruled the bomber's right side hand-brake metering valve malfunctioned. That depleted the brake system's accumulated hydraulic pressure, "rendering the aircraft's brake systems inoperative when the engines shut down."

The B-1 was returning to Ellsworth after participating in a Singapore air show. The crew turned back to Andersen after reporting an in-flight emergency, a hydraulic leak.

After safely landing, the crew got out of the plane because of concerns about fire. The plane then rolled into a pair of parked fire trucks.

According to the Air Force report, contributing factors included a slight decline on the taxiway and the inability of the firefighters to successfully clear the path of the rolling B-1B.

Investigators also said a "substantially contributing factor" was the loss of the No. 3 hydraulic system, which was "due to improper swage operations and post-task inspection" that caused the in-flight emergency.

The Associated Press in April reported that another Ellsworth B-1 apparently hit something and caught fire while taxiing at Al Udeid Air Base in Qatar. The four crewmen safely evacuated. Subsequent reports said a hydraulic failure caused the bomber to veer off the runway and catch fire, setting off munitions and leading to a serious of explosions heard in parts of the capital at Doha, more than 20 miles away.

On March 20, crews from Box Elder and Ellsworth extinguished several grass fires that apparently were caused by a B-1 that made an emergency landing at the base.