SAN JUAN CAPISTRANO, Calif. - A mechanic recently fired from a nuclear plant was arrested for allegedly threatening former co-workers. Authorities said they found a cache of more than 250 weapons in his home and a rented storage locker.

The 43-year-old man, whose name was not released, may have wanted revenge over losing his job at the San Onofre Nuclear Generating Station plant several weeks ago, authorities said.

Ray Golden, a spokesman for Southern California Edison, which runs the plant, would not say why the man was fired. He said the man had worked at the plant since 1984, but his access permit to the nuclear reactor area had been revoked in 1995 and never restored. Golden would not say why.

Several times since his firing, the man called to threaten supervisors and other employees at the plant in San Diego County, 65 miles south of Los Angeles, said Orange County sheriff's spokesman Jim Amormino.

"He said he had a lot of guns, and he was going to come back and shoot them," Amormino said. "He did threaten supervisors ... and anyone who had anything to do with his termination."

The man was arrested Tuesday at his Laguna Niguel home and booked for investigation of terrorist threats.

Golden said the man did not threaten the nuclear plant itself.

A woman at the suspect's house yesterday shouted through the door, "He's not guilty of this!" She would not comment further.

Officials found 54 weapons at the man's house and more than 200 at a storage locker he rented in San Juan Capistrano. The cache included tear gas, hand grenades and assault rifles.

The locker also contained 4,000 to 5,000 rounds of ammunition and four inert hand grenades lying next to a container of explosive powder. Some of the weapons are illegal, authorities said.

Two deputies at the storage unit were overcome by a yellowish vapor that officials later identified as military-grade tear gas, Amormino said. The deputies were taken to a hospital to be examined, and a hazardous material team was sent to the site.

"We take every threat serious, especially those from former employees of a nuclear power plant," Amormino said. "Is the person capable of carrying out the threat? Considering we found a cache of weapons and ammunition, we think the answer is yes."