MIDDLETOWN, Pa. (AP) — For the second time in two months, the Three Mile Island nuclear power plant has had an automatic shutdown.

Plant officials say the shutdown occurred at 2:20 p.m. Thursday and that the release of steam made a loud noise that was audible to nearby residents.

Operators are trying to determine the cause.

Exelon Generation spokesman Ralph DeSantis said a similar shutdown occurred Aug. 22. He said there is no threat to the public health or safety and that the shutdown did not interrupt electrical service. He also said there was no detectable level of radiation in the steam.

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