Tokyo Electric Power Co.(TEPCO) said early Saturday that some workers at the troubled Fukushima No. 1 nuclear power plant have been exposed to radiation higher than the allowable dose.

At a press conference, TEPCO officials said that the allowable upper limit of radiation was set at 100 microsievert for workers conducting an emergency operation.

Several members of staff at the plant have been exposed to radiation higher than the limit while working outside the facilities buildings, they said.

As radioactive leaks were an unprecedented emergency, the firm decided to raise the upper allowable doze to 150 microsievert, according to the TEPCO officials.

And TEPCO has decided that these sufferers of excessive radiation will no longer be set to on-site tasks in the nuclear plant, local media reported.

Faced with the risks and threats of radioactive leaks at the plant, the health ministry agreed to raise the upper limit to 250 microsievert for the plant staff in a bid to ensure they have adequate working hours, according to the reports.