Federal officials are investigating possible safety violations that might have caused a boiler to explode at a paper mill in Antioch, killing two men. The mill was shut down as a result. "The condition of that boiler is bad," Bert Crandall, a company employee and friend of the victims, said in the wake of the announcement of the investigation. "We tell them all the time the steam line is bad. It's ready to go." But Mel Mountain manager of the Louisiana-Pacific Fibreboard Corp. plant, said the facility, which opened in 1949, was not unsafe and called the accident the worst in its history. "I feel that our safety record is excellent and there definitely has never been anything of this magnitude," he said. Don Allendorf, administrator for the federal Occupational Safety and Health Administration's coastal region, said the investigation will take one to four weeks.