Tokyo Electric Power Co. admitted Tuesday what many experts had long suspected: The cores of reactors 2 and 3 at the Fukushima No. 1 nuclear plant likely melted down and dropped to the bottom of their pressure vessels, just as happened at unit 1.

However, temperature readings taken in the two units, now ranging from about 100 to 110 degrees, suggest that most of the melted cores remain inside the pressure vessels and have been cooled by injected water.

"Although the simulation says that the melted cores would damage the pressure vessels if the water level was lower, we think the damage is limited considering the temperature data of the pressure vessels," Tepco spokesman Junichi Matsumoto said at a news conference.