OSLO, Norway (AP) _ An offshore oil rig's anchors broke free of the seabed on Tuesday and it was adrift in the North Sea with 77 people aboard, a television station reported.

Rescue helicopters from the mainland were on their way to the Norwegian drilling rig, which had been working at the Snorre field, about 90 miles northwest of the city of Bergen, off Norway's west coast.

Citing rescue leaders, the commercial TV-2 network said the rig was dragging its anchors.

The rig is owned by Dolphin AS and was working for Norsk Hydro ASA. No other details were immediately available.