Oslo  - Over 150 crew were evacuated from a Norwegian oil rig after oil leaked into the North Sea presented the risk of an explosion, authorities said Saturday.

They later stated the immediate danger of explosion had abated - but the situation remained serious. Specialist vessels were heading to the rig to deal with the oil.

A core team of some 60 workers remained on the Statfjord A platform in Norwegian waters, said a spokesman for StatoilHydro, the platform's operators.

The dawn evacuation was carried out by helicopters, with crew taken to nearby rigs. The alarm was given when inspectors discovered gas escaping from one of the rig's supply shafts.

StatoilHydro operates three rigs in the Statfjord field, which produces 150,000 barrels of oil a day. (dpa)