Updated

An explosive device that went off before dawn Wednesday and damaged the Jackson County prosecutor's office in Medford, Ore., appeared to be a failed attempt to level the building, a police spokesman said.

The device shattered windows and damaged mainly the exterior of the building, said Lt. Mike Budreau of the Medford police. Nobody was hurt.

"I think that it's safe to assume that had this bomb went off as it was intended to, it would have most likely destroyed most of the building, and we believe that was the intent of the suspect," Budreau told the Medford Mail Tribune (http://bit.ly/1aTtdUX ).

Budreau said the device included what appeared to be a propane tank that was found burning in front of the district attorney's office after the explosion was reported about 4:30 a.m.

The device didn't fully detonate, he said, leaving the tank as a valuable clue for investigators. "But it did catch fire and emitted a large flame until it eventually burned out," he said.

Budreau says police are searching for a man who ran from an officer several blocks away.

"We're not sure if that is going to be related to this case or if it's going to be unrelated," he said.

The resulting fire from the blast did not spread to nearby buildings. The office is part of a cluster of government offices in downtown Medford.

Police cleared a large area around the office out of fears there might be other explosive devices, but tightened the closed area after none was found. The district attorney's office was closed for the morning.