Gold also traded lower on the Tokyo Commodity Exchange, triggering circuit breakers because of steep price drops.

WSJ: Gold Plummets to Two-Year Low

The company suspects the rodent may have caused a short-circuit in a switchboard, triggering the power cut.

BBC: Fukushima: Rat linked to outage at Japan nuclear plant

The company said a rat had damaged the electrics, causing a short circuit in a switchboard and triggering the power cut.

BBC: Fukushima nuclear plant: Cooling system power restored

Tepco officials said a rat had damaged the electrics, causing a short circuit in a switchboard and triggering the power cut.

BBC: IAEA calls for improvements at Japan's Fukushima plant

Officials said a circuit board and battery pack - parts of a triggering mechanism - had been recovered and the lid of a pressure cooker, apparently blown off during the explosion, was found on the roof of a nearby building.

BBC: Boston Marathon 'bombing suspect' seen on video