The boss at Japan’s Fukushima nuclear power plant is to step down this week due to ill health.

Masao Yoshida has been admitted to hospital and will officially quit his post as general manager of the plant on Thursday.

The nature of his illness is not known. However, there is speculation in Japan that it is related to the nuclear accident at Fukushima in March following an earthquake and tsunami and Yoshida’s subsequent exposure to radiation at the site.

According to Japanese newspaper Sankei Shimbun, Yoshida sent a message to workers at the plant, which stated: “A condition was discovered during a regular medical check the other day. I had no choice but to be hospitalised at very short notice for treatment under doctors’ advice.”

Takeshi Takahashi, who has headed nuclear power plant operations at Tokyo Electric Power Co, owner of the Fukushima, will take over as general manager of the plant on Thursday.