New Explosion at Fukushima No.2 reactor on March 15, 2011

Japan's Nuclear and Industrial Safety Agency says an explosion was heard early Tuesday morning at the No.2 reactor of the disaster-hit Fukushima No.1 nuclear power plant. Agency officials told reporters that the blast was heard at 6:10 AM local time on Tuesday.

Chief Cabinet Secretary Yukio Edano earlier told a news conference that a reactor facility, called the suppression pool, has been damaged. But agency officials said they have no detailed information yet about the report. They said that depending on where the damage is done, either liquid or air could leak out of the suppression pool.

The suppression pool is linked to the reactor containment vessel and is designed to prevent radioactive material from leaking outside. Experts say a breach to this crucial facility has raised the possibility of a radioactive leak. The Nuclear and Industrial Safety Agency also said that nuclear fuel rods inside the No.2 reactor are exposed above water by about 2.7 meters. That's about half the length of the fuel rods.

Agency officials said that radiation levels around the nuclear power plant reached 965.5 microsieverts following the explosive sound. They say the figure later dropped slightly to 882 microsieverts. The officials said they believe the rise in radiation level is due to the breach in the suppression pool, but that they cannot say for sure. They said they are monitoring the situation closely.

The officials added that the monitored level of radiation would not immediately pose a health threat. Tokyo Electric Power Company that operates the power station briefly evacuated workers from the facility following the sound of the blast.