Anti-pollution teams worked to contain a gasoline spill into the lake around Quai Wilson.
The alert was sounded yesterday morning when passers-by reported smelling petrol.
Firefighting teams put up inflatable barriers to stop the fuel spreading – the contamination was estimated to spread 200 meters wide and 100 meters long.
But the pollution is only going to have a limited impact on the ecosystem, says the canton.
An investigation into the leak is now underway.