Smoke was spotted again Tuesday morning at two reactors at the troubled nuclear power plant in northeast Japan's Fukushima Prefecture.

 Smoke was spotted again Tuesday morning at two reactors at the troubled nuclear power plant in northeast Japan's Fukushima Prefecture. [Video]

At around 6 p.m., white smoke was spotted rising from the No. 2 reactor, just two hours after the No. 3 reactor was seen spewing out gray smoke and forced workers nearby to evacuate.

The No. 3 reactor has been the top concern for Japan. The authority has been making fervent efforts to contain damage to the stricken facility and prevent further release of radioactive materials.

According to a Japanese nuclear safety official, there was no evident explosion, spike in radiation or injuries at the No. 3 reactor.

Tokyo Electric Power Co., the company in charge of the troubled plant, began to study the nuclear crisis' impact on the sea Tuesday.

On Monday, radiation was detected 1,600 times higher than normal levels in an area about 20 kilometers from the crippled plant, according to International Atomic Energy Agency.

An external power source became available Monday night for the No. 1 reactor, paving the way for electricity to be supplied to the reactor.