The operator of the crippled Fukushima No. 1 nuclear power plant in Japan, Tokyo Electric Power Co. (TEPCO), announced Tuesday that a partial fuel meltdown was confirmed at the No. 2 and No. 3 reactors at the facility in addition to the No. 1 reactor.

The utility said that the pressure vessels at the No. 2 and No. 3 reactors may have been damaged.

TEPCO said earlier in May that most of the fuel at the No. 1 reactor had melted down to the bottom of the pressure vessel.

The Japanese government and the utility have been battling to keep the plant crippled by the devastating earthquake and tsunami in March under control. It is still leaking radioactive substances into environment.