Workers are pumping nitrogen into one of the reactors at Japan's damaged nuclear plant in an attempt to prevent an explosion caused by dangerously overheated fuel rods.

Wednesday's crisis at the Fukushima plant came after technicians finally stopped a leak of highly radioactive water from the power station that dramatically increased the amount of radiation found in nearby ocean waters.

Chief Cabinet Secretary Yukio Edano said the water leak stopped before 6 a.m. Wednesday local time.  Until then, water samples in the vicinity had shown radiation levels up to 7.5 million times the allowable limit.

However, Edano said it is too early to say with confidence that the problem has been solved, and that officials from the Tokyo Electric Power Company are trying to determine whether radioactive water is leaking from any other location.