The operator of Japan's tsunami-wrecked nuclear power plant said a contract worker in his 60s died Saturday after collapsing at the facility's waste disposal building, adding that his body showed no signs of dangerous levels of radioactivity.

The man was carrying equipment at the Fukushima Dai-ichi nuclear plant when he collapsed. He died later in hospital, said Tokyo Electric Power Co. spokesman Naoyuki Matsumoto.

The company does not know the cause of his death, Matsumoto said. The man had begun working Friday at the waste disposal building, which stores radioactive-contaminated water that has leaked from the plant's tsunami-crippled reactors.

He had been wearing a radiation protection suit, mask and gloves, and no radioactivity at harmful levels was detected in his body, the spokesman said.

The Fukushima plant lost its power and cooling systems in the March 11 earthquake and tsunami, triggering fires, explosions and radiation leaks in the world's worst nuclear accident since Chernobyl in 1986.

The March disaster is believed to have killed more than 24,500 people. Police said Friday that 15,019 were dead and 9,506 were still listed as missing.

Radiation leaks at the Fukushima plant have forced 80,000 people living within a 20-kilometer radius of the nuclear facility to leave their homes.

The nuclear crisis at Fukushima has prompted the government to evaluate all of Japan's 54 reactors for quake and tsunami vulnerability, leading Prime Minister Naoto Kan to request a temporary shutdown of a nuclear power plant in central Japan.

Read more: 3news.co.nz