Estimated 10-Foot Tsunami is Seen Off Japan by Helicopter; Second Explosion Believed

DEVELOPING: Nuclear officials believe a hydrogen explosion has occurred at stricken Fukushima Dai-ich plant.

Soldiers and officials in northeastern Japan are warning residents that the area could be hit by another tsunami and are ordering residents to higher ground.

Sirens around the town of Soma went off late Monday morning and public address systems ordered residents to higher ground.

Kyodo News Agency said the tsunami could be 10 feet (3 meters) high, citing Fukushima prefectural officials.

An Associated Press reporter stood about 100 yards (100 meters) from the coast.

The area was hit by a massive quake and tsunami on Friday.