2nd explosion at Japanese nuclear plant

But the inner reactor container was intact after the explosion, said Yukio Edano, Japan's chief cabinet secretary, and little radioactivity was dispersed.

Officials said a second hydrogen explosion has occurred at the Fukushima Daiichi nuclear power plant in Japan, the Japanese broadcaster NHK reported Monday morning.

Tokyo Electric Power Co. said three people were injured and seven were missing in the explosion.

Interactive map Nuclear power plants affected by Japan quake and tsunami:

Residents within 20 kilometres of the plant had been advised to stay indoors, NHK said.
The explosion at the Fukushima Daiichi Unit 3 had been feared earlier Sunday.

Members of a local firefigher group carry the body of a victim in Rikuzentakata, Miyagi Prefecture, northern Japan, on Sunday, March 13, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (Kyodo News/Associated Press)

Evacuees walk through a flooded street in Ishinomaki, Miyagi Prefecture, on March 13, two days after an earthquake-triggered tsunami hit Japan's east coast. (Kyodo News/Associated Press)

Survivors receive medical treatment by doctors and nurses of the Japanese Red Cross's National Disaster Response Team at the Ishinomaki Red Cross Hospital on March 12, one day after the catastrophic earthquake and tsunami. (Toshiharu Kato/Japanese Red Cross Society/Associated Press)

A baby is fed milk by a member of the Japanese Red Cross's National Disaster Response Team at the Ishinomaki Red Cross Hospital on March 12. (Toshiharu Kato/Japanese Red Cross Society/Associated Press)

A Japan Self-Defence Forces helicopter fights a forest fire in Kamaishi, Iwate Prefecture, on March 13. (Kyodo News/Associated Press)

Members of a British search and rescue team sort their equipment as they arrive at the Misawa U.S. air force base in Misawa, Japan, on March 13. The approximately 70-strong team arrived in northern Japan to help in the aftermath of the earthquake and tsunami. (Matt Dunham/Associated Press)

A victim is carried on a stretcher at the Red Cross Hospital in Ishinomaki, Miyagi Prefecture, on Sunday. (Kyodo News/Associated Press)

Evacuees walk on a flooded street in Ishinomaki, Miyagi Prefecture, on March 13. (Kyodo News/Associated Press)

On Saturday, Unit 1 at the plant blew up, but little radiation leaked because the reactor container didn't break.
With the the cooling systems disrupted by the tsunami Friday, the heat had been building up.
Operators lost the ability to cool three reactors at Daiichi and three more at the nearby Fukushima Daini complex
They had been dumping seawater into Units 1 and 3, even though that will destroy the reactors.
On Monday morning officials had issued another tsunami warning for the same region that was devasted Friday, but quickly called it off.