Anti-nuclear groups, meanwhile, questioned the handling of the incident at the Tricastin nuclear site near Avignon, noting inconsistent official statements about when it occurred and about how much unenriched uranium was leaked.

France’s nuclear safety agency said liquid containing traces of unenriched uranium leaked from a factory at the site, and that uranium concentrations in the Gaffiere river were initially about 1,000 times the normal levels. The agency said the uranium is only slightly radioactive although toxic.

Initially the agency said the accident occurred Tuesday morning, but later said it occurred Monday night. On Wednesday, Tricastin authorities revised downward the amount of liquid that leaked.

Authorities in the Vaucluse region maintained a ban Wednesday on the consumption of well water in three nearby towns and the watering of crops from the Gaffiere and Lauzon rivers. Swimming, water sports and fishing also remain banned.

A series of tests Tuesday showed that “uranium levels (in surface water) remained well above normal but strongly diminished through dilution throughout the day,” the regional administration said in a statement. The tests found no uranium in groundwater.

Tricastin authorities changed the amount that had leaked from 7,900 gallons (30,000 liters) to 4,760 gallons (18,000 liters), according to another statement from the Vaucluse regional administration. It said the liquid contained 493 pounds (224 kilograms) of natural unenriched uranium, instead of 794 pounds (360 kilograms) announced earlier.

The factory handles materials and liquids contaminated by uranium, the fuel for nuclear power plants. The liquid spilled from a reservoir that overflowed during the washing of a tank.