Tokyo (CNN) -- Japan's nuclear safety agency on Friday worsened its assessment of problems at the Fukushima nuclear power plant as soldiers and utility workers continued a frantic effort to hose down overheating nuclear fuel with water cannons.
The Nuclear and Industrial Safety Agency raised the level from a 4 to 5 -- putting it on par with the 1979 incident at Pennsylvania's Three Mile Island.
According to the International Nuclear Events Scale, a level 5 equates to the likelihood of a release of radioactive material, several deaths from radiation and severe damage to a reactor core.
The Chernobyl nuclear accident in the former Soviet Union rated a 7 on the scale, while Japan's other nuclear crisis -- a 1999 accident at Tokaimura in which workers died after being exposed to radiation -- was a 4. The partial meltdown of a reactor core at Three Mile Island was deemed the worst nuclear accident in U.S. history.
