Two workers at Japan's damaged Fukushima Daiichi nuclear power plant have been taken to hospital after being exposed to high levels of radiation.
The pair had been attempting to restore the cooling system in reactor 3, which was damaged by the quake on 11 March.
Several workers have now been hurt on the site, an indication of the scale of the task facing them.
Radiation levels in Tokyo's water supply have now fallen, but remain high in other areas of northern Japan.
The official death toll from the magnitude 9.0 quake and subsequent tsunami has now risen to 9,523. Another 16,094 people are listed as missing.
Japan's nuclear safety agency said three workers had been injured when their feet came into contact with radiation-contaminated water while laying cables in the turbine area of reactor 3.
They were exposed to radiation levels of 170-180 millisieverts, he said, which is lower than the maximum level permitted for workers on the site of 250 millisieverts. Two of the workers were taken to hospital.
"Although they wore protective clothing, the contaminated water seeped in and their legs were exposed to radiation," said a spokesman.
"Direct exposure to radiation usually leads to inflammation and so that's why they were sent to the hospital to be treated."
Most people are exposed to 2 millisieverts over the average year, while 100 millisieverts is considered the lowest level at which any increase in cancer is clearly evident.
The condition of the injured workers was not immediately known.
Japan's chief cabinet secretary Yukio Edano said the situation was "very regrettable".
The power plant's cooling systems failed after the quake and tsunami, leading to the reactors overheating.
Power has now been restored to the site, but work to restart the coolers in reactor 3 was briefly suspended on Wednesday after a plume of black smoke was seen coming from it.
Tokyo Electric Power Co, which operates the plant, later allowed workers to re-enter after establishing there was no fire and that radiation level in the area had not risen.
The International Atomic Energy Agency (IAEA) said there had been some "positive developments" at the site but that the situation was still "of serious concern".
The plant is 250km (155 miles) north-east of the capital, Tokyo. The government has declared a 20km exclusion zone and evacuated tens of thousands of people. Those living up to 30km away have been told to stay indoors to minimise exposure.
People in Fukushima prefecture have been told not to eat 11 types of green leafy vegetables grown locally because of contamination worries. Local producers have been ordered not to send the goods to market.
Tokyo residents were warned on Wednesday not to give tap water to babies less than a year old because levels of radioactive iodine - which can cause thyroid cancer - are twice the recommended safe level in some areas of the city.
Officials stressed that children would have to drink a lot of it before it harmed them and urged people not to panic-buy. But supermarket shelves were reported to have been cleared of bottled water by Thursday morning.
"Customers ask us for water. But there's nothing we can do," Masayoshi Kasahara, a supermarket worker in Tokyo told Reuters.
"We are asking for more deliveries but we don't know when the next shipment will come."Emergency shelters
Radiation readings on Thursday showed levels in water in Tokyo had fallen back below the danger level, but the municipal authorities are distributing thousands of bottles of water to households with infants.
The authorities in the nearby city of Kawaguchi, Saitama prefecture, also reported radiation levels above safety norms in its water supply on Thursday.
Concern is also growing among Japan's neighbours. Australia has become the latest country to ban food imports from the affected region.
Police believe the final death toll from Japan's twin disaster may be more than 18,000.
Most of the deaths - 5,700 - have been reported in the prefecture of Miyagi. Three thousand bodies have been found in Iwate prefecture, and 776 in Fukushima.
At least 18,000 houses were destroyed and 130,000 damaged, and more than 200,000 people are living in emergency shelters.
The Japanese government has said it will cost as much as 25 trillion yen ($309bn; £189bn) to rebuild the country after the disaster.