(CBS News) -- Smoke billowed and orange flames rose from a nuclear plant on Monday (March 14) as a new hydrogen explosion rocked the plant damaged by a massive earthquake.
At least six people were injured in the blast, Tokyo Electric Power Co (TEPCO) said.
Officials said the blast at the No. 3 reactor of the Fukushima Daiichi plant was believed to be the same sort of explosion which occurred at the plant's No.1 plant on Saturday (March 13) and the core container was believed to be intact.
"There was a large sound from the No. 3 reactor at 11:01 a.m. and white smoke rose. We think it is a hydrogen explosion," Kaoru Yoshida, TEPCO Public Relations official told reporters.
"At 12pm. we have confirmed six injured and none missing. If you have any questions we will get back to you later," added Yoshida.
Officials repeatedly said it was unlikely the blast caused a large radiation leak and but the local government warned those still in the 20-km (13-mile) evacuation zone to stay indoors. Seven people, six of them soldiers, were missing in the blast, Jiji said.
TEPCO had earlier halted injection of sea water into the reactor, resulting in a rise in radiation levels and pressure. The government had warned that an explosion was possible because of the buildup of hydrogen in the building housing the reactor.
Officials confirmed on Sunday (March 13) that three nuclear reactors north of Tokyo were at risk of overheating, raising fears of an uncontrolled radiation leak.
Engineers worked desperately to cool the fuel rods in the damaged reactors. If they fail, the containers that house the core could melt, or even explode, releasing radioactive material into the atmosphere.
A badly wounded nation has seen whole villages and towns wiped off the map by a wall of water following a massive earthquake, leaving in its wake an international humanitarian effort of epic proportions.
Broadcaster NHK, quoting a police official, said more than 10,000 people may have been killed as the wall of water triggered by Friday's (March 11) 8.9-magnitude quake surged across the coastline, reducing whole towns to rubble. It was the biggest to have hit the quake-prone country since it started keeping records 140 years ago.