The United Nations nuclear watchdog chief says there might be limited core damage in a reactor at the Japanese power plant damaged by last week's earthquake.
International Atomic Energy Agency director general Yukiya Amano says there is a possibility of core damage - estimated at less than 5% - at the Fukushima Daiichi plant's number 2 reactor.
Mr Amano says recent developments in Japan's nuclear crisis are worrying but he still believes the situation is different from that of the 1986 Chernobyl disaster.
The agency earlier said Japanese data indicates radioactivity levels have fallen sharply at the Fukushima complex.
Professor Andrew Sherry, the Director of the Dalton Nuclear Institute at the University of Manchester, told Morning Report that it remains confusing how bad the damage to reactors is.
However, he says at this stage a catastrophic radiation leak looks unlikely.
There have been a series of explosions at the plant over the past four days.
A fire also briefly broke out at the number 4 reactor and is believed to have caused radioactive leaks.
Kyodo news agency says the Government has ordered the injection of water into a pool used to store spent nuclear fuel at that reactor.
Japanese media say the pool might be boiling, potentially causing the fuel to be exposed to the air and overheat.
The United Nations weather agency says winds are currently blowing radioactive material towards the ocean and there are "no implications" for Japan or countries nearby.
Residents flee area
People living in the Fukushima area are continuing to flood out of the city.
Residents within 20 kilometres of the plant have been told to evacuate and those 20 to 30 kilometres away are being urged to stay indoors and shut their windows.
Tauranga woman Jessica Harvey, who lives about 50 kilometres away with her husband and four-month-old daughter, have been taken to the Australian embassy in Tokyo.
She says her family had no fuel to drive out of Fukushima and the New Zealand embassy organised seats on a bus bound for the Australian embassy.
Ms Harvey told Morning Report she had just half an hour to make the decision to leave her home of three years and everything in it behind.
She says says the family only has the clothes they are wearing and a baby blanket and are hoping to get on a flight to New Zealand.
Another New Zealander Graham Clave also lives about 50 kilometres from the reactors.
He told Morning Report while he and his wife are ready to leave, they won't be doing so unless there is a catastrophic release of radiation.
The latest official death toll from the quake and tsunami is nearly 3400, but it is feared at least 10,000 may have been killed.
More than half a million people are living in temporary shelters which are short of water, food and fuel - while more freezing weather and snow is predicted for the days ahead.