Pilgrim Nuclear Power Station in Plymouth once again lost power Sunday, after having it restored for several hours following an offsite outage Friday night. Three diesel generators were providing backup power to the facility’s safety systems, said Carol Wightman, a spokeswoman for Entergy Corp., the Louisiana company that owns Pilgrim.

“There’s no worker or public safety concern,” she said. “We’re troubleshooting the cause.”

Wightman said workers were determining exactly what went wrong, but the outage may have been weather-related.

The plant was first shut down late Friday when it lost its “offsite power supplies” in the middle of the snowstorm. Electricity returned to Pilgrim at 10:55 a.m. Sunday, according to Entergy, but went back out later by the afternoon, and before the facility was returned to service.

Wightman could not say exactly when Pilgrim would be back online.

The shutdown is Pilgrim’s third this year, though the first two times — both in January — were caused by equipment issues at the plant, and not an offsite power loss.