TOKYO (AP) -- Just four hours after a tsunami swept into the Fukushima nuclear power plant, Japan's leaders knew the damage was so severe that the reactors could melt down, but they kept their knowledge secret for months. Five days into the crisis, then-Prime Minister Naoto Kan voiced his fears that it could turn worse than Chernobyl.
The revelations were in documents released Friday, almost a year after the disaster. The minutes of the government's crisis management meetings from March 11 -- the day the earthquake and tsunami struck -- until late December were not recorded and had to be reconstructed retroactively.
They illustrate the confusion, lack of information, delayed response and miscommunication among government, affected towns and plant officials, as some ministers expressed the sense that nobody was in charge when the plant conditions quickly deteriorated.
The minutes quoted an unidentified official explaining that cooling functions of the reactors were kept running only by batteries that would last just eight hours.
"If temperatures in the reactor cores keep rising beyond eight hours, there is a possibility of meltdown," the official said during the first meeting, which started about four hours after the magnitude-9.0 earthquake and ensuing tsunami hit the Fukushima Dai-ichi plant, setting off the crisis.
Apparently the government tried to play down the severity of the damage. A spokesman for the Nuclear and Industrial Safety Agency was replaced after he slipped out a possibility of meltdown during a news conference March 12.
The plant operator, Tokyo Electric Power Co., acknowledged a partial meltdown much later, in May.
Top government spokesman Yukio Edano, who is now trade minister, urged other ministers to watch what they said to the public.
"We must provide information fast, but it must be accurate," Edano said on March 14. "We must be clear about all our evaluations and judgment, and announce them only after we reach a decision."
While then-trade minister Banri Kaieda suggested on March 11 that residents within a (6-mile) 10-kilometer radius might have to be evacuated, the government ordered 1,800-plus residents within a 1.2-mile (2-kilometer) zone to leave. Then that expanded to 5 miles (3 kilometers), then to 6 miles (10 kilometers) within two hours, and finally to 12 miles (20 kilometers) the next day.
Kan said a 12-mile (20-kilometer) zone would suffice. After seeing a series of explosions and fires at reactor buildings, Kan on March 16 cautioned his Cabinet about the possibility that the Fukushima crisis could be worse than the Chernobyl accident in 1986.
Kan was particularly concerned about a spent fuel pool inside the No. 4 reactor building, which had the largest number of fuel rods and rising water temperatures.
"We should worry about the Unit 4 pool, whose temperature has been on the rise," he said, adding that other spent fuel pools at Fukushima Dai-ichi, as well as four others at the neighboring Dai-ni plant, could also deteriorate.
"The amount of radiation that could be released from those reactors could be larger than Chernobyl. We must keep cooling the reactors, whatever it takes. It's going to be a long battle," he said, according to the minutes dated March 16.
It was nearly 10 days before one of his top nuclear advisers produced a worst-case scenario at his request. The March 25 paper, produced by the head of the Japan Atomic Energy Commission, warned that a disaster of that scale would require evacuating 30 million people from the greater Tokyo area. Fearing panic, the government kept the report a secret, but The Associated Press obtained it in January.
The failure to properly record the minutes of the government's crisis management meetings has added to sharp public criticism about how the nuclear crisis was handled, deepening distrust of politicians and bureaucrats.
"Who is the leader of the actual operation? I get too many requests and appeals that are incoherent," Yoshihiro Katayama, internal affairs minister at the time, said at a March 15 meeting. "Nobody seems to be in charge."
The minutes also showed top crisis managers were confused, causing miscommunication that left local officials and residents without crucial information needed for evacuation. The ministers used a list of people who needed assistance for evacuation and their details by quoting Japanese media, not firsthand information from local authorities.
Yukiya Amano, director general of the International Atomic Energy Agency, said it was not just natural disasters that caused the Fukushima crisis. He said accident command lines were unclear and response plans were not sufficiently integrated. Amano also cited the nuclear regulator's weak oversight, insufficient guard against possible risks such as total power loss and inadequate training to respond to serious accidents.
But Fukushima provided a lesson for the rest of the world and nuclear safety is stronger than a year ago, he said in a statement Friday from Vienna.
"Human failings such as these are not unique to Japan," Amano said. "We humans learn from our mistakes."