Japanese authorities detected high level of radioactivity at a reactor in the troubled Fukushima No. 1 nuclear power plant on Sunday, local media reported.

In addition, more than 1,000 millisieverts per hour was found in the water at the No. 2 reactor Sunday. That's 10 million times the radioactivity level when the reactor is operating normally.

The operator Tokyo Electric Power Co said the extremely contaminated water may come from the damaged fuel in the reactor.

Japanese authorities also found radioactive iodine 134 was extremely high in water at the reactor. Workers working at the reactor were temporarily evacuated due to the high radiation.

Radioactive iodine which is 1,850 times the legal limit was found in sea near the troubled plant, according to Kyodo. The level had surpassed the figure detected near the drain outlets of the plant on Saturday.

The government's Nuclear and Industrial Safety Agency has found radioactive iodine 1,250.8 times above legal limit in sea near the plant on Saturday. The readings were taken Friday morning about 330 meters south of the plant, near the drain outlets of the reactors at the utility.

The agency added that the radiation will not have a significant impact on fishery products because fishing is not conducted in the area within 20 km of the plant.

Japanese authorities have been stepping up efforts to fix the nuclear power plant crippled by devastating March 11 earthquake and tsunami.