A series of problems and misunderstandings contributed to the Bourbon Dolphin disaster, which claimed eight lives when the oil-rig support tug capsized 75 miles north-west of Shetland in April.

Among them was a failure of an emergency release mechanism - or failure to operate it properly - which should have disengaged the anchor chain attached to the Transocean Rather oil rig which dragged the boat over on its side.

Although this came late in the sequence of events which contributed to the disaster, it is thought a faster emergency release may have averted it.

There was also confusion over which direction another anchor-handling vessel should have been pulling the chain in what was meant to be a routine anchor-laying procedure. Eight of the 15 Norwegian crew, including a father and his 14-year-old son died in the tragedy.

Only three bodies were recovered.

The Norwegian Justice and Police Minister, Knut Storberget, appointed a five-strong commission to investigate the cause of the tragedy off Shetland and is due to report in full on February 1, 2008.

Among the commission's interim recommendations are improving knowledge of the emergency release system on the winch.

It is thought that the button that triggers the release may not have been depressed long enough by the crew members.

The commission also called for more information about boat stability and better regulations covering anchor-laying procedures involving more than one boat working in tandem.