(Corrects to make clear ownership of Oskarshamn plant) STOCKHOLM, May 21 (Reuters) - Swedish state energy firm Vattenfall said the Oskarshamn nuclear plant received a bomb threat on Wednesday, and a source at the plant said a building had been sealed after an employee was found carrying unauthorised explosives. Police said they were questioning a suspect at the plant but could not immediately confirm he was an employee of the facility. The Oskarshamn plant is owned by Germany's E.ON and Finland's Fortum.
