The company said smoke was detected in the turbine building of reactor No. 1 at the Fukushima Daini nuclear power plant around 6 p.m. (5 a.m. ET).
Smoke could no longer be seen by around 7 p.m. (6 a.m. ET), a company spokesman told reporters.
The Fukushima Daini nuclear power plant is about 10 kilometers (6 miles) from the Fukushima Daiichi nuclear power plant, where workers have been scrambling to stave off a meltdown since the March 11 earthquake and tsunami knocked out cooling systems there.
Tokyo Electric Power Co. owns both plants.
After the dual disasters, Japanese authorities also detected cooling-system problems at the Fukushima Daini plant, and those living within a 10-kilometer radius (6 miles) of Fukushima Daini were ordered to evacuate as a precaution.
Hundreds were protesting on Wednesday outside the Tokyo headquarters of Tokyo Electric Power Co , the operator of the earthquake-crippled Fukushima nuclear plant in northeast Japan.
Protestors were chanting “Stop nuclear power”.
The Japanese Nuke Meltdown is being equated to Chernobyl in terms of plutonium release. See the video here.