Recent tests conducted on rivers in Southern France showed that uranium levels are diminishing but have not vanished after a leak from a nuclear site resulted in water contamination, regional authorities said Wednesday.

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 to 4,760 gallons, according to another statement from the Vaucluse regional administration. It said the liquid contained 493 pounds of natural unenriched uranium, instead of the 794 pounds 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.

The Commission for Independent Radioactivity Research and Information said the leak led to the release of radioactive material 100 times that which the site is allowed to release in a year. Greenpeace said the leaked waste was more than 130 times the permitted level.