Updated

FUKUSHIMA, Japan -- A worker hired to help bring the crippled Fukushima nuclear plant under control died suddenly, the third fatality reported among workers at the stricken plant since the March accident, The Wall Street Journal reported Friday.

Plant operator Tokyo Electric Power Co. (TEPCO) said it believed the death Thursday, like the previous two, had nothing to do with exposure to radiation in the plant. It also said the death did not result from overwork, though the company did not disclose the cause.

TEPCO said a male worker in his 50s became ill during a meeting Wednesday morning, before his shift started. He was taken to a hospital immediately, and died the next morning.

"We can't disclose what was cited as the cause on his death certificate because it would amount to violation of privacy," a TEPCO spokesman said.

Following the accident, set off by the March 11 earthquake and tsunami, TEPCO was criticized for insufficient attention to worker conditions, subjecting dozens of workers to dangerous levels of radiation. In March, six workers were exposed to over 250 millisieverts of radiation -- the ceiling set for emergency workers at the plant -- including two who sustained suspected radiation burns to their legs after wading through contaminated water without wearing boots.

Safety records improved significantly in recent months -- In July, only six workers received doses of between 20 and 50 millisieverts, compared with 1,264 who were exposed to at least 20 millisieverts in March.

The two other deaths among Fukushima workers came in May, when a man died of a heart attack, and in August, when a man died of an acute form of leukemia after working for just seven days at the plant.

In both cases, TEPCO said the death was unrelated to the man's work at the plant.

The worker who died this week had worked there since Aug. 8, helping to install a tank used to treat contaminated water. He spent a total of 46 days at the plant, logging an average three hours a day. His accumulated dose of radiation exposure was two millisieverts, well below the 250-millisievert ceiling.

A Sept. 9 whole-body scan of the man had shown no excessive exposure, the spokesman said. TEPCO was still waiting for a test result to see if the worker had experienced more internal exposure since.

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