(Reuters) - Japan's nuclear crisis appeared to be spinning out of control on Wednesday after workers withdrew briefly from a stricken power plant because of surging radiation levels and a helicopter failed to drop water on the most troubled reactor.
In a sign of desperation, police will try to cool spent nuclear fuel at one of the facility's reactors with water cannon, normally used to quell riots.
Early in the day, another fire broke out at the earthquake-crippled facility, which has sent low levels of radiation wafting into Tokyo in the past 24 hours, triggering fear in the capital and international alarm.
Japan's government said radiation levels outside the plant's gates were stable but, in a sign of being overwhelmed, appealed to private companies to help deliver supplies to tens of thousands of people evacuated from around the complex.
"People would not be in immediate danger if they went outside with these levels. I want people to understand this," Chief Cabinet Secretary Yukio Edano told a televised news conference, referring to people living outside a 30-km (18-mile) exclusion zone. Some 140,000 people inside the zone have been told to stay indoors.
The European Union's energy chief, Guenther Oettinger, told the European Parliament that the plant was "effectively out of control" after breakdowns in the facility's cooling system.
Workers cleared debris to build a road so fire trucks could reach reactor No. 4 at the Daiichi complex in Fukushima, 240 km (150 miles) north of Tokyo. Flames were no longer visible at the building housing the reactor.
High radiation levels prevented a helicopter from dropping water into the No. 3 reactor to try to cool its fuel rods after an earlier explosion damaged the unit's roof and cooling system.
The plant operator described No. 3 -- the only reactor at that uses plutonium in its fuel mix -- as the "priority." Plutonium, once absorbed in the bloodstream, can linger for years in bone marrow or liver and lead to cancer.
The situation at No. 4 reactor, where the fire broke out, was "not so good," the plant operator added, while water was being poured into reactors No. 5 and 6, indicating the entire six-reactor facility was now at risk of overheating.
"Getting water into the pools of the No.3 and No.4 reactors is a high priority," Hidehiko Nishiyama, a senior official at Japan's Nuclear and Industrial Safety Administration, told a news conference, adding the pool for spent fuel rods at No. 3 was heating up while No.4 remained a concern.
"It could become a serious problem in a few days," he said.
A military helicopter may be used again to try to drop water and troops mobilized to help pump water by land, he said.
Nuclear experts said the solutions being proposed to quell radiation leaks at the complex were last-ditch efforts to stem what could well be remembered as one of the world's worst industrial disasters.
"This is a slow-moving nightmare," said Dr Thomas Neff, a physicist and uranium-industry analyst at the Massachusetts Institute of Technology.