Tohoku Electric Power Co. on Saturday reported a leak of coolant water from a nuclear power plant between the towns of Onagawa and Oshika, Miyagi Prefecture.

It said plant workers discovered a pool of water on the floor near a coolant water filtering device in the building that houses the turbine for the Onagawa plant's No. 1 reactor at around 10:45 a.m.

A subsequent inspection showed that water was leaking from the vicinity of a valve on a pipe on one of six filters. About 1 liter of water had leaked out, but no radiation was found to have escaped from the plant, the power firm said.

The water registered radiation levels of roughly 5,000 becquerels, far short of the 3.7 million becquerels which would require notification to authorities, according to Tohoku Power.