Stockholm - Reactor one at Sweden's Oskarshamn nuclear power plant was shut down overnight after two contractors there were arrested on suspicion of planning sabotage at the plant.

The shutdown was "purely a precautionary measure," OKG, the operator of the three-reactor plant on Sweden's south-eastern coast, said Thursday.

Police in Kalmar also reported incriminating material was found during searches of the suspects' houses. They did not release details.

The two men were arrested Wednesday after traces of an explosive were detected during a spot security check of a bag carried by one of the men, a welder, as he tried to enter the plant, plant spokesmen and police said.

After the discovery, police explosives experts searched the plant. A plant spokesman said in a radio interview Thursday morning that the search was continuing and so far had turned up nothing suspicious.

The plant, which is operated by the energy groups E. ON of Germany and Finland's Fortum, produces about 10 per cent of Sweden's energy. (dpa)