Police in Japan have begun investigating Monday's nuclear power plant accident. Four workers died and several were injured in the accident, although authorities say there is no sign that radiation leaked from the Mihama plant.
Police are investigating whether negligence may have contributed to the deadly accident at the 28-year-old Mihama nuclear power plant.
A small condenser pipe burst Monday afternoon, sending deadly jets of steam into a crowd of workers.
The plant's operator says safety precautions at the site might not have been fully obeyed. Plant managers say the pipe that ruptured was last inspected in 1996. The managers had delayed checks until later this month and say they never expected such rapid corrosion.
Company officials also said that a private inspection company notified the plant in April that the pipe was overdue for a thorough safety check.
Yohsaku Fuji, president of Kansai Electric Power, which owns the plant, apologized for the tragedy.
Mr. Fuji says the victims' families want officials to find out what went wrong and make sure nothing like this can happen again.
In addition to the fatalities, seven workers were also injured. One remains in critical condition with severe burns over 80 percent of his body.
Prime Minister Junichiro Koizumi has ordered a full investigation into the incident. And local police say nearly one hundred officers are gathering evidence at the plant, about 320 kilometers west of Tokyo.
Economy Minister Shoichi Nakagawa, whose ministry is responsible for Japan's nuclear industry, has also apologized for the accident.
Mr. Nakagawa says the prime minister has insisted that the public have full access to all the facts of the case.
Japan relies on nuclear energy for nearly one-third of its electric power. But a series of accidents, safety violations and cover-ups has undermined public confidence in Japan's nuclear industry.
Japan has 52 nuclear plants and the national government hopes to build 11 more by 2010.