(Corrects to make clear ownership of Oskarshamn plant)

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STOCKHOLM, May 21 (Reuters) - Swedish state energy firm Vattenfall said the country's Oskarshamn nuclear plant had received a bomb threat on Wednesday, and a source at the site said a building was sealed off after an employee was found carrying explosives.

Police said they were questioning a suspect at the Oskarshamn plant, south of Stockholm on the Baltic coast, but could not immediately confirm he was an employee of the facility.

"There has been a bomb threat at Oskarshamn (nuclear plant). I hope to have more information about this in the next hour or hours," Vattenfall spokesman Torsten Bohl said.

A security source at the plant, who spoke on condition of anonymity, said officials had sealed off one of the buildings at the facility.

"We have sealed off 300 metres around one building," the source said.

Oskarshamn, which is owned by Germany's E.ON and Finland's Fortum, is one of three nuclear plants in Sweden that meet half the country's power needs.

Vattenfall operates Sweden's two other nuclear plants. (Editing by Keith Weir)

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