An 80-year-old woman and her teenage grandson are rescued nine days after Japan's devastating earthquake and tsunami.

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A teenage boy and his 80-year-old grandmother have been rescued from a house nine days after it was hit by the quake and tsunami in Japan, as officials said the death toll was likely to rise above 21,000.

News of the rescue of Sumi Abe and her grandson Jin filtered through as the Government said two units at Japan's stricken Fukushima nuclear plant had been safely cooled, though pressure unexpectedly rose in a third reactor and traces of radiation were found in more food.

Sumi and Jin, 16, were rescued from a demolished house in Ishinomaki, Miyagi Prefecture, yesterday, nine days after a catastrophic earthquake and ensuing tsunami hit northeastern Japan, police told Kyodo News.

The pair were not injured but Jin was taken to Ishinomaki Red Cross Hospital suffering from hypothermia or abnormally low body temperature, Kyodo reported.

Their family and rescue workers had been searching for them after they received a call from the boy saying that the two were stranded in the house. However, they were unable to initially find the house as it was washed away by the tsunami.

While they were looking for survivors in the city, four police officers found the boy who was on the roof of the demolished house calling for help.

The pair told the police that they have been stranded at the house since the massive quake hit the area on March 11, and had been eating yoghurt and drinking water and coke stored in the refrigerator.

The boy's father Akira, 57, said: ''I'm so glad that the two hung tough. For the past nine days, I've always believed that they were alive.''

According to Akira, the boy managed to make one 50-second call on his cellphone. He told his brother on the phone that, although the house had been demolished, he and his grandmother were alive and staying in the kitchen on the second floor.

A pressure increase at the Fukushima plant's third reactor may force its operators to deliberately release radioactive steam, prolonging a nuclear crisis that has consumed the Government's attention even as it responded to the catastrophic earthquake and tsunami that savaged northeast Japan on March 11.

Beyond the disaster area, uncertainty grew over the safety of food and water. The government halted shipments of spinach from one area and raw milk from another near the nuclear plant after tests found iodine exceeded safety limits. But the contamination spread to spinach in three other prefectures and to more vegetables _ canola and chrysanthemum greens. Tokyo's tap water, where iodine turned up on Friday, now has cesium. Rain and dust are tainted too.

In all cases, the government said the radiation levels were too small to pose an immediate risk to health. Still, Taiwan seized a batch of fava beans from Japan found with faint _ and legal _ amounts of iodine and cesium.

''I'm worried, really worried,'' said Mayumi Mizutani, a 58-year-old Tokyo resident shopping for bottled water at a supermarket to give her visiting 2-year-old grandchild. ''We're afraid because it's possible our grandchild could get cancer.'' Forecasts for rain, she said, were an added worry.

All six of the Fukushima Dai-ichi nuclear complex's reactor units saw trouble after the disasters knocked out cooling systems. In a small advance, the plant's operator declared reactors 5 and 6 - the least troublesome - under control after their nuclear fuel storage pools cooled to safe levels.

Progress was made to reconnect two other units to the electric grid and in pumping seawater to cool another reactor and replenish it and a sixth reactor's storage pools.

But the buildup in pressure inside the vessel holding Unit 3's reactor presented some danger, forcing officials to consider venting. The tactic produced explosions of radioactive gas during the early days of the crisis.

''Even if certain things go smoothly there would be twists and turns,'' Chief Cabinet Secretary Yukio Edano told reporters. ''At the moment, we are not so optimistic that there will be a breakthrough.''

Nuclear safety officials said one of the options could release a cloud dense with iodine as well as the radioactive elements krypton and xenon.

The plant's operator, Tokyo Electric Power Co., temporarily suspended the plans yesterday after it said the pressure inside the reactor stopped climbing, though staying at a high level.

''It has stabilised,'' Tokyo Electric manager Hikaru Kuroda told reporters.

Kuroda, who said temperatures inside the reactor reached 572 degrees Fahrenheit (300 degrees Celsius), said the option to release the highly radioactive gas inside was still under consideration if pressure rose.

Growing concerns about radiation add to the overwhelming chain of disasters Japan has struggled with since the 9.0-magnitude quake. The quake spawned a tsunami that ravaged the northeastern coast, with 8,100 people officially confirmed dead (authorities believe the number will climb above 21,000), leaving 12,000 people missing, and displacing another 452,000, who are living in shelters.

Fuel, food and water remain scarce. The government in recent days acknowledged being caught ill-prepared by an enormous disaster that the prime minister has called the worst crisis since World War II.

''The recent bodies _ we can't show them to the families. The faces have been purple, which means they are starting to decompose,'' said Shuji Horaguchi, a disaster relief official setting up a centre to process bodies in Natori, on the outskirts of Sendai.

''Some we're finding now have been in the water for a long time, they're not in good shape. Crabs and fish have eaten parts.''