An 82-car Southern Pacific freight train derailed in an industrial section of Manteca, forcing the precautionary evacuation of 150 to 200 people from homes and businesses, officials said. Railroad officials said 48 cars were knocked from the tracks and three of them contained residue from chlorine, phosphoric acid and hydrocarbons, which prompted the evacuation order. No one was hurt and most of the evacuees were allowed to return to the area after several hours. Four cars that did not derail contained military ordnance and were later taken to Oakland. Mike Irvine, an SP division superintendent, said the train was traveling at 50 m.p.h. when the locomotive's weight snapped a rail bolt, causing the derailment. Police said the limited evacuation of an eight- to nine-block area was ordered because chemical residue in the three tanker cars could have posed a threat.