French Polynesia has urged France to study the risk of a huge wave that could be triggered by the collapse of the former French nuclear weapons testing site in Mururoa.
In a letter to the president of France, Nicolas Sarkozy, the French Polynesian president, Gaston Tong Sang, has asked Paris to send experts to the area rapidly to assess the risks and suggest solutions.
The letter says that according to a French nuclear safety official, an atoll collapse could trigger a 20-metre wave and expose people on Tureia atoll to radiation levels 300 times higher than in France.
Mr Tong Sang says there is disquiet, fear and anger among the people, and he has urged Paris to set up a warning system.
Last year, the nuclear test veterans organisation Moruroa e tatou warned of possible contamination because part of Moruroa has sunk.