Workers are checking if there is any damage to equipment at the No.1 to No.4. reactors. Lights in the No.2 reactor's control room are expected to be switched on again on Friday.

The Fukushima office of Tokyo Electric Power Company says the surface temperature of the No.1 reactor dropped to about 205 degrees Celsius on Friday morning. It had risen to about 400 degrees, exceeding the safety limit of 302 degrees.

TEPCO also says the pressure inside the container vessel of the No.1 reactor dropped to 0.31 megapascals from 0.385 on Thursday morning.

In the turbine building of the No.3 reactor, work is under way to drain the highly radioactive water that 3 staff members were exposed to on Thursday. Its radiation level was 10,000 times higher than those for water inside the reactor.