Japan declared states of emergency for five nuclear reactors at two power plants after the units lost cooling ability in the aftermath of Friday's powerful earthquake. Thousands of residents were evacuated as workers struggled to get the reactors under control to prevent meltdowns.

A single reactor in northeastern Japan had been the focus of much of the concern in the initial hours after the 8.9 magnitude quake, but the government declared new states of emergency at three other plants in the area Saturday morning.

The earthquake knocked out power at the Fukushima Daiichi plant, and because a backup generator failed, the cooling system was unable to supply water to cool the 460-megawatt No. 1 reactor. Although a backup cooling system is being used, Japan's nuclear safety agency said pressure inside the reactor had risen to 1.5 times the level considered normal.

Authorities said radiation levels had jumped 1,000 times normal inside Unit 1 and were measured at eight times normal outside the plant. They expanded an earlier evacuation zone more than threefold, from 3 to 10 kilometers (2 miles to 6.2 miles). Some 3,000 people had been urged to leave their homes in the first announcement.

The government declared a state of emergency, its first ever at a nuclear plant. And plant operator Tokyo Electric Power Co. warned of power shortages and an "extremely challenging situation in power supply for a while."

The utility, which also operates reactors at the nearby Fukushima Daini plant, later confirmed that cooling ability had been lost at three of four reactors there, as well as a second Fukushima Daiichi unit. The government promptly declared a state of emergency there as well.

The reactor core remains hot even after a shutdown. If the outage persists, it could in a worst-case scenario cause a reactor meltdown, an official with Japan's nuclear safety agency said on condition of anonymity, citing sensitivity of the issue.

Japan Nuclear and Industrial Safety Agency official Ryohei Shiomi said radiation levels inside the control center at the Fukushima Daiichi No. 1 reactor have surged to 1,000 times normal, while a monitoring device at the front gate of the compound detected radiation that is eight times higher than normal.

The level outside the 40-year-old plant in Onahama city, about 170 miles (270 kilometers) northeast of Tokyo, is still considered very low compared to the annual exposure limit, Shiomi said. It would take 70 days of standing at the gate to reach the limit, he said.

Shiomi said radioactive vapor probably entered the control room because of lack of air flow control resulting from power outage. The control room is usually radiation free, protected by negative air pressure. If the condition persists or worsens, the plant is equipped with gas masks and other protective gear to protect workers from radiation exposure, he said.

Officials planned to release slightly radioactive vapor from the unit to lower the pressure in an effort to protect it from a possible meltdown, but the continuing power supply problem has delayed the process.

Chief Cabinet Secretary Yukio Edano said the amount of radioactive element in the vapor would be "very small" and would not affect the environment or human health. "With evacuation in place and the ocean-bound wind, we can ensure the safety," he said at a televised news conference early Saturday.

The agency said plant workers are scrambling to restore cooling water supply at the plant but there is no prospect for immediate success.

Another official at the nuclear safety agency, Yuji Kakizaki, said that plant workers were cooling the reactor with a secondary cooling system, which is not as effective as the regular cooling method.

Kakizaki said officials have confirmed that the emergency cooling system _ the last-ditch cooling measure to prevent the reactor from the meltdown _ is intact and could kick in if needed.

"That's as a last resort, and we have not reached that stage yet," Kakizaki added.

Edano said both the state of emergency and evacuation order around the Fukushima Daiichi plant are precautionary measures.

"We launched the measure so we can be fully prepared for the worst scenario," he said. "We are using all our might to deal with the situation."

Defense Ministry official Ippo Maeyama said the ministry has dispatched dozens of troops trained for chemical disasters to the Fukushima plant in case of a radiation leak, along with four vehicles designed for use in atomic, biological and chemical warfare.

Pineville, La., resident Janie Eudy said her husband, Danny, was working at Fukushima No. 1 when the earthquake struck. After a harrowing evacuation, he called her several hours later from the parking lot of his quake-ravaged hotel.

He and other American plant workers are "waiting to be rescued, and they're in bad shape," she said in a telephone interview.

Danny Eudy, 52, a technician employed by Pasadena, Texas-based Atlantic Plant Maintenance, told his wife that the quake violently shook the plant building he was in. "Everything was falling from the ceiling," she said.

Eudy told his wife that he and other workers were evacuating the plant when the tsunami swept through the area, carrying away homes and vehicles. They retreated so they wouldn't get caught up in the raging water.

"He walked through so much glass that his feet were cut. It slowed him down," she said.

After the water started to recede, Eudy and other workers drove to their hotel, only to find it in shambles.

"Most of the hotel was gone," she said. "He said the roads were torn up and everything was a mess."

His hotel room was demolished along with all of his belongings, so Eudy had to borrow a resident's phone to call his wife early Friday morning. The workers were waiting for daylight but contemplating seeking higher ground in case another big wave hit.

"He sounded like he was in shock. He was scared," Janie Eudy said. "They're totally on their own, trying to just make it."

Neil Sheehan, a spokesman for the U.S. Nuclear Regulatory Commission, said staff were trying to collect more information on what was happening.

At the Fukushima Daiichi site, "They are busy trying to get coolant to the core area," Sheehan said. "The big thing is trying to get power to the cooling systems."

Speaking at the White House, Secretary of State Hillary Clinton also said U.S. Air Force planes were carrying "some really important coolant" to the site, but administration officials later said she misspoke. The U.S. offered such help but the Japanese said they didn't need it, the officials said, speaking on condition of anonymity because they were not authorized to speak publicly on the matter.

High-pressure pumps can temporarily cool a reactor in this state with battery power, even when electricity is down, according to Arnold Gundersen, a nuclear engineer who used to work in the U.S. nuclear industry. Batteries would go dead within hours but could be replaced.

The nuclear reactor was among 10 in Japan shut down because of the earthquake.

The Fukushima plant is just south of the worst-hit Miyagi prefecture, where a fire broke out at another nuclear plant. The blaze was in a turbine building at one of the Onagawa power plants. Smoke could be seen coming out of the building, which is separate from the plant's reactor, Tohoku Electric Power Co. said. The fire has since been extinguished.

Another reactor at Onagawa was experiencing a water leak.

The U.S. Geological Survey said the 2:46 p.m. quake was a magnitude 8.9, the biggest earthquake to hit Japan since officials began keeping records in the late 1800s.

A tsunami warning was issued for a number of Pacific, Southeast Asian and Latin American nations.

At the two-reactor Diablo Canyon plant at Avila Beach, Calif., an "unusual event" _ the lowest level of alert _ was declared in connection with a West Coast tsunami warning. The plant remained stable, though, and kept running, according to the NRC.

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AP National Writer Jeff Donn reported from Boston. Associated Press writers Michael Kunzelman in New Orleans and Matthew Lee in Washington contributed to this report.