“A worker at our company spotted smoke emerging from the brake of the hoisting function of a crane in a turbine room,” the operator Tokyo Electric Power Co (TEPCO) said in a statement.

“We reported immediately to the fire station and used fire extinguishers and now the smoke has stopped.”

“There were no injuries nor any radiation leak” resulting from the incident in the Kashiwazaki-Kariwa nuclear plant, in Niigata prefecture, 200 kilometres north of Tokyo, it said.

The company said it would thoroughly investigate.