KIEV, Ukraine (AP) _ A reactor at the Zaporizhska nuclear power plant shut down automatically because of a short circuit in a transformer, a plant official said today.

The plant's No. 4 reactor went off-line Thursday when a plant safety system detected the short circuit, spokesman Oleh Osheka said. There was no change in radiation levels within or around the reactor, he added.

Osheka said freezing weather may have caused power cables to ice over. The Zaporizhska plant, 250 miles southeast of Kiev, has six nuclear reactors. Three are operational.