Three hundred engineers have been battling inside the danger zone to salvage the six-reactor Fukushima plant in the world's worst nuclear crisis since Chernobyl 25 years ago.

Encouragingly for Japanese transfixed on work at the Fukushima complex, the most critical reactor -- No. 3, which contains highly toxic plutonium -- stabilized after fire trucks doused it for hours with hundreds of metric tons of water.

Work also advanced on bringing power back to water pumps used to cool overheating nuclear fuel, and Kyodo news agency reported that temperatures at spent fuel pools in reactors No. 5 and 6 were returning to normal.

Technicians attached a power cable to the No. 1 and No. 2 reactors, hoping to restore electricity later in the day prior to an attempt to switch the pumps on. They aim to reach No. 3 and 4 soon after that.

If successful, that could be a turning point in a crisis rated as bad as America's 1979 Three Mile Island accident. If not, drastic measures may be required such as burying the plant in sand and concrete, as happened at Chernobyl in 1986, though experts warn that could take many months and the fuel had to be cooled first.

On the negative side, evidence has begun emerging of radiation leaks from the plant, including into food and water. Traces exceeding national safety standards were, though, found in milk from a farm about 30 km (18 miles) from the plant and spinach grown in neighboring Ibaraki prefecture.

The Japanese government ordered additional tests and depending on the results may ban sales and shipments of food products from areas in the vicinity of the plant.

Reuters