New quake hits Japan, rocking buildings in Tokyo (UPDATES)

A tsunami warning followed a 7.1-magnitude aftershock off Japan on Thursday nearly a month after a 9-0-magnitude quake and tsunami flattened the northeastern coast.

The Japan meteorological agency issued a tsunami warning for a wave of up to 6 feet for a coastal area already torn apart by last month’s tsunami, according to the Associated Press.

Buildings as far away as Tokyo, 215 miles away, shook for about a minute from the quake, which reportedly struck 25 miles under the water off the coast of Miyagi prefecture — 90 miles from Fukushima, where the stricken nuclear plant is located.

About 28,000 people are dead or missing, and hundreds of thousands were left homeless after the tsunami ripped through Miyagi prefecture, according to the BBC.

According to CBS, officials at Tokyo Electric Power Co., said the aftershock had caused "no problems" at the Fukushima Dai-ichi nuclear complex, where workers have been struggling to contain radiation since the tsunami. Workers had been evacuated to safe ground.

But NHK World TV reported that external electrical power supply had been cut in two of the three lines servicing the Ongawa nuclear power plant in the Miyagi prefecture because of the quake. Only one line was now in service to continue to cool down the nuclear fuel, according to the Japan's Nuclear and Industrial Safety Agency.

And the New York Times quoted experts as saying that a big aftershock posed an additional risk to the Fukushima plant because its containment structures were filled with water for use in the cooling efforts. That water was now highly radioactive, and the strain from holding that water could make the structures more vulnerable to rupture in the event of an earthquake.

Hundreds of aftershocks have shaken the northeast region devastated by the March 11 earthquake, but few have been stronger than 7.0. 

A Pacific Tsunami Warning Center evaluation of the quake said an oceanwide tsunami was not expected, according to the AP.