Workers are close to restoring power to cooling systems at a quake-hit Japanese nuclear power plant, officials say.
Engineers connected a cable through which they hope to supply electricity to part of the Fukushima Daiichi plant.
The earthquake and tsunami it triggered crippled the plant's cooling systems, and some radiation has leaked.
More than 8,000 people are now known to have died in the 11 March disaster, with more than 12,000 still missing, police say.
Radioactive contamination has been found in some food products from the Fukushima prefecture, Japanese officials say.
The iodine was found in products - reported to be milk and spinach - tested between 16 and 18 March and could be harmful to human health if ingested, the officials said.
International nuclear experts at the IAEA say that, although radioactive iodine has a short half-life of about eight days, there is a short-term risk to human health if it is ingested, and it can cause damage to the thyroid.
The IAEA had earlier reported on its website that food products from Fukushima prefecture had been banned from sale by the Japanese authorities, but later said a ban was only being considered.
Traces of radioactive iodine have also been found in tapwater in Tokyo and five other prefectures, officials said on Saturday.
The traces are within government safety limits, but usual tests show no iodine, the AP news agency reported.
Meanwhile, radiation has been detected for the first time in Japanese imports, with Taiwanese officials finding contamination in a batch of fava beans, although they say the amount is too small to be dangerous to humans.
The earthquake and tsunami are now known to have killed 8,133 people, while 12,272 remain missing.
On Sunday, police said they believed 15,000 people had been killed in Miyagi prefecture - one of the hardest hit regions - alone.
It is looking increasingly clear that the death toll will top 20,000 people at least, says the BBC's Rupert Wingfield-Hayes in Tokyo.
The disaster dwarfs anything Japan has seen since World War II and people are beginning to talk of the disaster in similar terms, says our correspondent.
The authorities have begun building temporary homes for some of the hundreds of thousands of people still sheltering at emergency evacuation centres.
Many survivors have been enduring freezing temperatures without water, electricity, fuel or enough food.
Japan has been shaken by scores of tremors since 11 March - one of magnitude 6.1 hit the Ibaraki area south of Fukushima on Saturday. There were no immediate reports of any damage.
At the stricken plant, firefighters have continued to spray water at the dangerously overheated fuel rods, in a desperate attempt to avert a meltdown.
Engineers hope that restoring power will allow them to restart pumps to continue the cooling process.
Japan's nuclear safety agency earlier hoped that electricity would be restored on Saturday but later revised its projection.
"If no problem is found at the facility today, the power will resume as early as tomorrow [Sunday], " agency spokesman Fumiaki Hayakawa is quoted by the AFP news agency as saying.
However, an official from the power company which runs the plant told AFP: "Although we are doing our best, unfortunately we cannot say when electricity will be restored."
Given the scale of the damage, it is not certain the cooling systems will work even if power is restored.
However, Kyodo news agency said the cooling system had already been reactivated at reactor 6 and temperatures in one spent-fuel pool had dropped.
Meanwhile emergency workers spent Saturday night spraying the most vulnerable reactors with water.
On Friday officials raised the level on a seven-point international scale of atomic incidents from four to five.
The crisis, previously rated as a local problem, is now regarded as having "wider consequences".
Radiation levels have risen in the capital Tokyo, 240km (150 miles) to the south, but officials say the amounts found are not harmful.
Meanwhile, reports that a young man had been found in a wrecked house eight days on from the quake have proved false, after it emerged that he had in fact returned to his ruined home from an evacuation centre.
Katsuharu Moriya, a man in his 20s, was found on Saturday by emergency workers in the city of Kesennuma, in Miyagi prefecture.
Millions of people have been affected by the 9.0-magnitude quake and tsunami; as many as 400,000 people are living in basic temporary shelters in cold temperatures and with little food.
The government has now conceded it was too slow in dealing with the nuclear crisis.
Chief Cabinet Secretary Yukio Edano accepted that "in hindsight, we could have moved a little quicker in assessing the situation and co-ordinating all that information and provided it faster".
Prime Minister Naoto Kan has sought to form a crisis cabinet to tackle reconstruction, but the leader of Japan's conservative opposition rejected an offer to join a grand coalition.
Mr Kan said in a television address on Friday: "We will rebuild Japan from scratch. We must all share this resolve."