At 1:51pm on August 23, 2011, a 5.8 magnitude earthquake occurred, centered south of Mineral, Virginia, eleven miles from the North Anna Nuclear Station. The Associated Press reported the quake "was felt as far north as Rhode Island, New York City and Martha's Vineyard, Mass." The reactors automatically shut down and, because of a loss of offsite power, four diesel generators started up to supply electricity to safety systems. The plant reported an "Alert" status, the second lowest level of four NRC emergency classifications, until 11:16am on August 24, 2011. One of the generators suffered a coolant leak and stopped working. A fifth standby generator was activated to replace the broken unit, which was repaired. Offsite power was restored later on August 23. Dominion also reported that the aftershocks did not affect the power plant. Also on August 24, Dominion announced that it had ended the "Notice of Unusual Event", the least serious of the NRC emergency classifications, at the North Anna Power Station following inspection of equipment susceptible to seismic activity.