A methane gas explosion ripped through an evacuated sewer tunnel under construction in Milwaukee, killing three workmen who had reentered the shaft to check whether it was safe for other workers to return. Rescue workers found the bodies of two men about 2,000 feet from the entrance of the 30-foot-deep tunnel more than five hours after the blast. The third body was recovered several hours later from the same area. Project manager Patrick Doig said methane inside the tunnel exploded, but officials did not yet know what touched off the blast. The three men were among about 10 workers who were in the tunnel at 8:30 a.m. when a detector on a mining machine indicated high levels of potentially explosive gases, particularly methane, Doig said.