Tokyo's government began distributing mineral water to mothers with young babies on Thursday, a day after elevated levels of radiation were found in the city water supply. Bottled water is one of several items in short supply in the Japanese capital.
Japan's government appealed to people not to hoard water, but the request apparently fell on deaf ears.
Bottled water was virtually impossible to find in Tokyo on Thursday.
Stores and vending machines had been cleared out the previous evening, after the government disclosed that levels of radioactive iodine in tap water were above the safe level for babies.
On Thursday afternoon, Tokyo said the level had dropped back below the safe limit for babies.
But that news came as two bordering cities, Kawaguchi to the north and Matsudo to the east, said radiation levels in their water were now unsafe for babies.
Water is one of several items in short supply in Tokyo, almost two weeks after the earthquake.
At the Maruetsu supermarket in central Tokyo, there is plenty of meat, fish and vegetables. But what you will not find is toilet paper, disposable diapers, milk or instant ramen. Eggs are again available, limited to one box per family.
Japan's Chief Cabinet Secretary, Yukio Edano, says the government is working to increase the supply of bottled water.
Edano says he will ask drinks makers to increase production and the government might look overseas to import water.
But increasing the supply might be difficult, as many companies are already at full capacity so they can supply disaster-hit north Japan.