( ABC NEWS ) By AKIKO FUJITA, LEEZEL TANGLAO and JESSICA HOPPER
Japanese authorities have declared a state of emergency at another nuclear power plant following Friday's massive earthquake that has left the country in a crisis Japan hasn't seen since World War II.
A state of emergency was declared at the Onagawa nuclear power plant, located in the hard-hit Miyagi prefecture, the International Atomic Energy Agency reported.
Following Friday's 8.9 magnitude earthquake, a fire broke out at the Onagawa plant but was later contained, the Associated Press reported. Officials from the Tohoku Electric Power Company said that higher than normal radioactivity readings prompted the heightened alert today. The emergency is at level one, the lowest state of emergency.
Officials in Miyagi are still digging through smoldering debris and collapsed homes and buildings left in the aftermath of Friday's 8.9 magnitude earthquake and tsunami. One official estimates that up to 10,000 people could be dead in Miyagi alone.
At least 1,596 people have been killed, according to NHK News.
Japanese authorities are frantically working to prevent a meltdown at a series of nuclear reactors 156 kilometers away in Fukushima. The United States' Nuclear Regulatory Commission has sent two of its officials with expertise in boiling water nuclear reactors.
There is increasing concern about Unit 3 at the Fukushima Daiichi power plant. Workers released radioactive air and injected sea water to reduce pressure and cool the reactor down, Chief Cabinet Secretary Yukio Edano said.
Edano warned of the possibility of another hydrogen explosion at the plant. On Saturday, an explosion at Unit one injured four workers.
"At the risk of raising further public concern, we cannot rule out the possibility of an explosion," Edano said. "If there is an explosion, however, there would be no significant impact on human health."
Already, at least 170,000 people have been evacuated in the 12 mile radius around the Fukushima plants. It is unclear if people are being asked to evacuate around the Miyagi power plant. Doctor Michio Kaku, a physicist, said that Japan should consider extending the evacuation orders.
"Winds don't stop blowing at 12 miles...computer models show that the radiation doesn't disperse in a sphere or a circle. It disperses in a plume, a pencil-like plume that then waves with the wind like a lighthouse," Kaku said.
Officials anticipate another earthquake of 7.0 magnitude or greater in the coming days, possibly further damaging the already fragile nuclear reactors.
"If there's a secondary earthquake, that could tip the whole thing over. Pipes could break, leaks could take place and even as you put sea water in, the water could bleed out, creating a full scale meltdown. That's the nightmare scenario," Kaku said.
Another nuclear complex, the Tokai Dai-Ni plant, experienced a failure after Friday's quake, the Associated Press reported. It's not clear why the incident wasn't reported by the Japan Atomic Power Co. until Sunday.
"Disaster in the Pacific": Watch "Good Morning America" and "World News" for special coverage of the Pacific earthquake and tsunami on Channel 7.;