British air accident investigators are due to arrive in Libya to help authorities there discover what caused the air crash which killed five Britons.

The crash in the Mediterranean off the Libyan coast killed 22 passengers, including British oil workers Patrick Cox, John Morton, Thomas McNeilly, Ronald Jarred and Roy Parfitt.

Crash experts from Farnborough flew out to the North African country after Libya accepted an offer of help, the Foreign office has confirmed.

The Belfast-built Shorts SD-360 was carrying 38 passengers from Tripoli to an oil refinery at Marsa el Brega when it suffered a catastrophic breakdown.

One Briton is among five people still missing from the crash as storms in the Mediterranean hampered recovery efforts.

The Swiss owners of the aircraft, Avisto, said it was lying four to five kilometres off the coast in 30 metres of water.

Ahmed Aoun, chairman of Sirte Oil, the company which employed the workers and leased the aircraft, said 15 divers from the off-shore search team had been unable to leave harbour on Saturday due to bad weather.

"Chances of survival are becoming slimmer and slimmer but we will not give up hope today because the marine team has not been able to go out," said Mr Aoun.

"Once they have been able to go off-shore we can assess the situation according to their findings."

Fuel system failure?

The British experts' role is expected to focus on claims that the fuel system may have been at fault, causing both the twin-engined plane's Pratt & Whitney turbo-prop engines to fail simultaneously.

Survivors have spoken of how the Libyan crew warned passengers that both engines had failed and their only chance was to ditch in the sea.

Aviation expert David Learmount, of Flight International magazine, said Britain would have been involved in the accident investigation because the Shorts SD-360 is a British-built aircraft.

"The British Civil Aviation Authority was the lead certificating authority for that aeroplane when the aeroplane was going through all its tests, before it was allowed to be sold to any airline," he said.

"It was the CAA that certified it was a safe piece of kit."