SAN CLEMENTE (CBS) — A partial shutdown of the San Onofre nuclear power plant was in effect Wednesday after sensors detected a possible leak in one of the reactor units.

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Jennifer Manfre with Southern California Edison told KNX 1070 there is no immediate danger to the public or to Edison workers after a sensor indicated a possible leak into a steam generator tube in Unit 3.

A spokesman for the Nuclear Regulatory Commission confirmed that some radioactive gas apparently leaked into an auxiliary building. It is unclear if any of it was released into the atmosphere, and if any did, it would have been a “very, very low level of radioactivity” that would be “barely measurable.”

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The shutdown comes as Unit 2 at the plant is currently offline for a previously scheduled maintenance, refueling and technology upgrade outage.

However, the shutdown of both units will not be a factor in determining when Edison will put Unit 3 back online, Manfre said.

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“It’s an investigation, and it’ll take time, and of course we’ll want to do that to ensure safety before bringing it online again,” she said.