TOKYO, March 14 (Xinhua) -- A second hydrogen explosion on Monday rocked the quake-stricken nuclear plant in Japan, as the government is going all-out to prevent a nuclear disaster.

Plumes of white smoke were seen coming from the Fukushima No.1 nuclear power plant following a loud explosion at the plant's No. 3 reactor, the Nuclear and Industrial Safety Agency (JNISA) said.

Tokyo Electric Power Co. said seven people went missing and 11 were injured after the explosion.

The agency said the wall of the reactor building collapsed, confirming eye-witness reports that only the building's skeletal structure remained.

The likelihood of high levels of radiation in the area is low, the agency said, but warned the 600 people who were still in the 20-km evacuation zone to leave immediately.

The agency also said large amounts of hydrogen have amassed in the upper parts of the reactor building, where the pressure remained unusually high, similar to that of the No. 1 reactor building, which also exploded on Saturday.

Cooling operations at the reactor were continuing to preserve the containment unit, although coolant levels were low, the agency reported.

JNISA had independently verified, however, that the containment vessel in the reactor was still intact.

Speaking at an emergency press conference Monday, Chief Cabinet Secretary Yukio Edano said the explosion did not damage the reactor and the containment vessel and that there was little possibility of mass radiation being leaked into the air.

Edano expressed concern on Sunday that a hydrogen explosion could occur at the plant's No. 3 reactor -- the latest reactor to face a possible meltdown, following a hydrogen blast on Saturday in the plant's No. 1 unit.

A TV station also reported a new tsunami on Monday but it turned out to be a false alarm.

While struggling to avert a nuclear meltdown, the government is also striving to take care of millions of survivors who are still without drinking water, electricity and proper food following Friday's catastrophic 9-magnitude earthquake and ensuing massive tsunamis.

A total of 1,647 people had been killed by 12:00 a.m. (0300 GMT) Monday, the National Police Agency confirmed.

But the death toll is likely to rise significantly, as latest reports from Kyodo News said about 2,000 bodies were found Monday on two shores in Japan's Miyagi Prefecture.

About 1,000 bodies were found washed ashore on Miyagi's Ojika Peninsula and another 1,000 were spotted in the town of Minamisanriku where the prefectural government has been unable to contact some 10,000 people, or over half the local population, the reports said.

The Miyagi prefectural government has decided to ask for help from other prefectures as work to cremate bodies is falling behind, according to the reports.

Miyagi, with a population of about 2.3 million, was one of the hardest hit areas.

While the country is grappling with the widespread damage, countries around the world have also offered help to Japan in dealing with the aftermath of the devastating earthquake.

At least 50 countries and regions have promised to provide relief support, and offers from over 70 specialized rescue teams from around the globe have been received by Japan.

A 15-member Chinese rescue team, which arrived in Japan around midday on Sunday, was set to start search and rescue operations Monday morning in Ofunato city of Japan's northeastern Iwate Prefecture.

China also pledged 30 million yuan (4.57 million U.S. dollars) worth of emergency humanitarian assistance to Japan to help the disaster relief there, the Chinese Ministry of Commerce said Monday.

South Korea dispatched five rescuers and two search dogs on Saturday, and another team of rescue workers left for Japan on Monday to help with the search and rescue efforts there.

Some organizations in Singapore are also offering help to those affected by the quake in northeastern Japan.