Nuclear plant worker dies of acute leukemia

http://mdn.mainichi.jp/mdnnews/news/20110830p2g00m0dm084000c.html
"TEPCO said the man had been involved with duties on radiation control at the plant for a week starting in early August. He later complained of poor health and underwent medical checkups before his death"

No internal exposure was found and this death is not from the work he did as an employe of tepco ...so
Why would u develop acute leukemia

"Most of the time, there is no obvious cause. However, the following may play a role in the development of leukemia in general:

Certain chromosome problems
Exposure to radiation, including x-rays before birth
Past treatment with chemotherapy drugs
Receiving a bone marrow transplant
Toxins such as benzene"

http://www.nlm.nih.gov/medlineplus/ency/article/000541.htm