UPDATE -- To see the most up-to-date information on Tuesday's San Onofre power plant emergency, please click here.
An emergency was declared at the San Onofre nuclear generating station on Tuesday afternoon. The threat turned out to be an ammonia leak, not a a nuclear one, and officials say it does not pose any public danger.
Workers discovered the ammonia leak just before 3pm, reports NBC LA. Southern California Edison spokesman Steve Conroy told NBC LA that no nuclear material was released, and there is no danger to the public.
As a precaution, the company evacuated employees in the area near where the leak was found... Other employees remain in other areas of the plant. There's no immediate danger to the public. Those units are operating normally.
According to the Associated Press, Southern California Edison spokesman Gil Alexander said that today's alert was the lowest of the four possible emergency classifications used by the nuclear industry. Alexander didn't know the size of the ammonia leak, but it came from a unit in the power plant that generates electricity. It is separate from radioactive systems at the plant.
The official twitter account of the San Onofre Nuclear generating station did not tweet anything about the emergency alert, the threat it posed, or the official statement about the ammonia leak.
In an October interview with KPBS, Alexander had said, "tell all your listeners to go check out @SCE_SONGS on Twitter... because Twitter is going to be the only way they are going to be able to get information in case of a real emergency."
The power plant signed up for Twitter after the nuclear disaster in Fukushima, Japan.
CORRECTION: A previous version of this story relayed inaccurate reports that the San Onofre nuclear plant had issued a level 3 alert on the International Nuclear Events scale. This is incorrect, and we regret the mistake.