The Fukushima nuclear plant in Fukushima prefecture in northeastern Japan is pictured in a 2008 file photo. (Xinhua/Kyodo file photo)
TOKYO, March 12 (Xinhua) -- The Japanese government confirmed Saturday that while an explosion did occur at the Fukushima No. 1 nuclear power plant earlier in the day, the blast did not happen at the location of its No. 1 reactor.

Chief Cabinet Secretary Yukio Edano said at an emergency press conference convened in Tokyo that owner and operator of the nuclear facility, Tokyo Electric Power Co., has confirmed that the steel container housing the reactor is intact.

Edano said that the blast, which occurred at 3:36 p.m. local time (0636 GMT), destroyed the roof and the walls of the reactor's outer container.

Authorities added that whilst the evacuation zone has been increased from a 10-kilometer radius for the Fukushima No. 1 and the troubled No. 2 plants to a 20-kilometer radius, no serious damage occurred to the container of the No. 1 reactor, as previously feared.

Japan's Nuclear and Industrial Safety Agency had said earlier that the reactor in the Fukushima No. 1 power station, located about 220 km north of Tokyo, may be starting to melt down after Japan's biggest earthquake on record hit the area Friday.

Recent reports, however, suggest the catastrophe may not be quite as deadly as previously thought.

Eye witnesses accounts and TV footage in Saturday afternoon showed smoke billowing from the site and reported that the reactor building had been destroyed, leading many to believe a partial core meltdown had occurred.

Four people have been injured at the power plant, authorities said, but radiation levels dropped quickly after surging, following the blast according to official accounts.

Prefectural officials in the area announced that the hourly radiation from the troubled plant reached 1,015 micro sievert in the vicinity prior to the explosion and that the radiation approximates an ordinary amount for an adult to be exposed to in one year.

The reports of the explosion followed aftershocks and came amid a mammoth search and rescue mission launched in the northeastern region of Japan involving both Japanese and U.S. military forces.

The Nuclear and Industrial Safety Agency confirmed that measures taken to release the potentially devastating build up of pressure had worked, essentially averting a nuclear meltdown and that radiation amount will pose no imminent health issues for nearby residents.

The agency also said that the wind currently blowing toward the sea rather than inland in the region is a helpful factor.

Government officials said that in the wake of Friday's colossal earthquake and tsunami that struck the northeastern region of Japan, 1,700 people are feared missing or dead.

Editor: Fang Yang