Japan has informed the International Atomic Energy Agency (IAEA) that a spent fuel storage pond at an earthquake-hit reactor is on fire and radioactivity is being released directly into the atmosphere, the Vienna-based U.N. atomic watchdog said.

Japan told the IAEA that dose rates of up to 400 millisievert per hour have been reported at the Fukushima Daiichi nuclear power plant site. The Japanese authorities are saying that there is a possibility that the fire was caused by a hydrogen explosion, IAEA said.

The IAEA said it is seeking further information on these developments, adding it continues to liaise with the Japanese authorities and is monitoring the situation as it evolves.

The powerful earthquake, the largest earthquake recorded in the country, struck Japan on Friday which was followed by a devastating tsunami and subsequent threats of a nuclear outbreak and volcanic activity.