Japan has raised the severity rating of its nuclear disaster

Japan has raised the severity rating of its nuclear disaster, as firefighters continue efforts to cool highly radioactive fuel rods at a nuclear reactor complex crippled by last week's earthquake and tsunami.

Japan on Friday increased the severity of the crisis at the Fukushima site from 4 to 5 on a 7-point international nuclear event scale.

Firefighters are dousing water on damaged reactor buildings with powerful hoses.  But they have to limit their time inside the complex due to the high radiation levels.

Japanese engineers also are extending an emergency power cable to the nuclear reactor complex.  A steady supply of power could enable workers at the Fukushima plant to get water pumps working again.

Meanwhile, the head of the International Atomic Energy Agency, Yukiya Amano, says Japan is racing against time to cool the overheating reactors.  Amano arrived in Japan Friday to meet with top Japanese officials and learn how the IAEA can help with the crisis.  

The increase in the nuclear accident's severity rating comes shortly after the chief secretary of Japan's cabinet, Yukio Edano, tried to calm fears about the radiation.  He said elevated radiation levels detected kilometers away from the plant were not a health risk.