The amount of radiation that leaked from the crippled Fukushima nuclear power plant in the first week after the disastrous tsunami struck is more than double the original estimate, according to the country’s nuclear safety agency.

Japan's Nuclear and Industrial Safety Agency (NISA) now estimates that 770,000 terabecquerels escaped into the air just after the catastrophe hit on March 11 – versus its earlier estimate of 370,000 terabecquerels.

BBC reports that the amount of radiation released is only about 15 percent of the total leakage from the Chernobyl disaster in 1986 – still the implication is that contamination around the site is worse than expected.

According to an official inquiry by an independent expert panel, the agency also concluded that meltdowns at three of the plant’s reactors occurred more rapidly that initially believed.

Specifically, NISA found that in reactor No 1, molten nuclear fuel fell to the bottom of the pressure vessel within five hours of the quake - 10 hours earlier than initially estimated.

Also, a meltdown damaged the No 2 reactor after 80 hours, and the No 3 reactor 79 hours after the tsunami destroyed the plant's coolant systems.

Meanwhile, the plant's operator, Tokyo Electric Power Co. (TEPCO), wants to close the Fukushima site by January 2012, however that too may be delayed since radiation is still leaking from the facility.

Eighty-thousand residents living within a 12-mile radius of Fukushima have been evacuated. Beyond that radius, a voluntary evacuation is being observed.

The new findings will only increase the criticism of the Japanese government and of TEPCO both for their failure to provide timely and accurate information on the nuclear disaster.