Six workers at the crisis-hit Fukushima Daiichi nuclear power plant have been exposed to radiation levels beyond the limit applied to an emergency operation, Tokyo Electric Power Co. said Saturday, without elaborating on the work that they were engaged in.

They are continuing to work on different tasks because they have not shown any abnormal signs since being exposed to over 100 millisieverts of radiation, the utility said. The limit has been raised to 250 millisieverts for the ongoing crisis, the worst in Japan's history, by the Health, Labor and Welfare Ministry.

The government's Fire and Disaster Management Agency said separately that readings of up to 27 millisieverts of radiation were detected as of noon on around 50 employees of the Tokyo Fire Department who were decontaminated after spraying water earlier in the day at the plant's highly dangerous No. 3 reactor.