Officials are now searching for the cause of an ammonia leak that triggered an emergency alert Tuesday at the San Onofre nuclear power plant in San Clemente, Calif.

They say the leak never posed any threat to the public, caused no injuries, and released no radioactive material. The plant's two units are now operating normally, the officials said.

Beachgoers on the sand near the San Onofre nuclear power plant in San Clemente, Calif., in June. (Lenny Ignelzi/AP)

The emergency alert, an unusual occurrence at a power plant, was required because fumes could prevent access to other areas of the plant.

About 25 gallons of ammonia were leaked in a non-nuclear part of the facility and collected in a basin underneath the tank. Exposure to high levels of ammonia can result in irritation, lung damage, serious burns, and even death. Ammonia is used at the plant to treat water that becomes steam, which helps produce electricity.

The plant, about 45 miles north of San Diego, is jointly owned by Edison, San Diego Gas and Electric and the city of Riverside.

The San Onofre plant was thrust into the spotlight back in March after the Japan earthquake and tsunami, when concerned residents pointed out that the station was near a fault line and sat on the edge of the sea.

While a spokesman for California Edison at the time said the station was protected by a 25-foot-high “tsunami wall” and had been built to withstand a 7.0 magnitude quake, the blog Boing Boing pointed out that the Japan tsunami’s waves were 33 feet high and that the quake clocked in at a 9.0.