At least 15 people were today injured after an explosion at a steel plant in central Japan, the latest in a series of accidents at the site.
Television pictures showed clouds of black smoke billowing from the Nippon Steel and Sumitomo Metal facility in Tokai, which employs 3,000 people.
A spokesman for the Aichi prefectural police said the fire department had been alerted to a problem at the plant at 12:46 pm (0346 GMT).
A Tokyo-based spokeswoman for the world's number-two steelmaker said the blast injured its workers and those from partner firms.
All 15 injured people were taken to hospital, according to a Tokai city emergency official.
"We don't know the severity of their injuries," he told AFP.
Five people suffered serious injuries from apparent smoke inhalation and burns, national broadcaster NHK reported.
It added that police would investigate the case over possible professional negligence that resulted in injury.
Factory workers were trying to deal with smoke rising from a coal storage unit near a coke oven before the blaze erupted, according to NHK, citing police sources.
"There was a small explosion that was caused by a fire at a coke oven," another Tokai city official told AFP.
Coal-based coke is a key ingredient used in the steelmaking process.
The explosion came after other fire troubles earlier this year. No one was hurt in separate incidents in January, June and July at the same plant
The incidents prompted the mayor of Tokai, a city of about 100,000 people, to formally ask the steelmaker to draw up a plan to deal with any safety problems.
Mayor Atsuo Suzuki submitted the request twice in the wake of separate incidents, according to local media.
Four incidents this year were related to power blackouts, the company spokeswoman said, adding that today's problem was caused by another issue.
"The fire broke out during the process right before coal is thrown into a coke oven," she said.
Unlike in neighbouring China, industrial accidents are relatively rare in Japan where safety measures are usually strictly enforced.
Last month, the plant announced preventative measures, including setting up a committee to investigate details of past incidents and overhauling the site's power supply systems.
