Two workers were killed and a third was badly injured in an accident Friday on a North Sea platform used by GDF Suez SA (GSZ.FR) to extract natural gas, the French power group said.

The accident happened during pressure tests on the L5A platform that stands about 100 kilometers north of the Dutch city of
Den Helder , a spokesman for the company said.

The injured worker was taken to a hospital and is being treated, he said, adding that all other employees have been accounted for.

Details of the accident remain sketchy but the group said the platform was not in production at the time.