Japan resumed dousing its crippled nuclear plant early on Sunday after an overnight break of several hours, officials said, as they pushed on with a desperate effort to avert an atomic catastrophe.
Fire trucks from the Self-Defense Forces had just started aiming their high-pressure water jets at reactor four of the ruined Fukushima plant, said a nuclear safety agency official at around 9am (0530 IST).
The Tokyo fire department -- which ended more than 13 hours of hosing operations at 3:40am (0010 IST Saturday) at the number three reactor -- were due to also resume operations today, an official said.
The firefighters unleashed 2,000 tonnes of water from three unmanned vehicles yesterday after some 50 firefighters had set up the equipment to minimise human exposure to high radiation, officials and local media said.
"We will resume operations today," Kazuya Kuwazuka, a Tokyo fire department spokesman, said, adding that no firefighters engaged in the operation had been exposed to unusually high levels of radiation.
The stricken plant, located 250 kilometres (155 miles) northeast of Tokyo, was one of four damaged by the massive March 11 earthquake and tsunami.
The twin disasters knocked out the plant's reactor cooling systems, sparking a series of explosions and fires. Authorities have since struggled to keep the fuel rods inside reactors and fuel storage containment pools under water.
If the heating rods are exposed to air, they could degrade further and emit large amounts of dangerous radioactive material.
Engineers have also sought to restore electricity to the reactors' cooling systems, although it was not yet clear whether these would function properly even if the power comes back on.