Tokyo ? About 105 gallons of coolant water containing radioactive material leaked from an inactive nuclear power reactor in western Japan, but there was no danger of radiation escaping from the plant, its operator said Tuesday.

The leak was discovered by a worker who rushed to the scene after an alarm went off at Reactor No. 3 of the Mihama nuclear power plant, about 200 miles west of Tokyo, according to Kansai Electric Power Co. spokesman Hiroshi Toshikiyo.

The water, which contained traces of radiation, spilled from the primary coolant tank into a catchment area, and about seven gallons then spilled onto the surrounding floor.

No radiation leaked outside the compound, and no one was harmed by radiation, Toshikiyo said. The cause of the leak was under investigation, but it appeared water spilled out after workers failed to properly attach a hose leading to the tank, he said.