PART of a military helicopter has been dragged up in nets by a trawler off the Western Isles. None has been reported missing.

There was speculation last night that the find, reported by a French trawler, could explain the alleged UFO seen plunging into the sea off Lewis two years ago.

The RAF last night confirmed it had launched an investigation after the helicopter rotor head with four blades, and part of a gearbox, was dredged up from a depth of 1000ft in a position about 80 miles west of the Butt of Lewis.

The trawler, the Albert Granet, was believed to be making for Stornoway last night with what could be part of a Westland helicopter. Only last month, part of the BBC1 programme Mysteries with Carol Vorderman was devoted to accounts from witnesses of the sightings north-west of the Butt of Lewis.

The RAF last night insisted: ''None of our aircraft is missing.'' No helicopters have been reported lost or missing in the area for decades. RAF spokesman Craig Lindsay did, however, confirm serial numbers from the recovered cluster indicated it was from a helicopter made by Westland.

The twin-engined Westland Lynx, used by many worldwide forces, is often used in maritime reconnaissance and operates well from aircraft carriers. It also has four rotor blades.

The find will fuel speculation the military knows more than it is saying about the incident on Saturday, October 26, 1996, off Ness.

Flashes and explosions in the sky were reported by a number of credible witnesses. A large-scale military exercise was under way and there were even claims a rogue missile had been deliberately destroyed.

A sea and air search covering 1000 square miles was launched after the witnesses reported seeing flashes and smoke and hearing two explosions. It was initially thought obvious an aircraft had crashed and police, coastguards, and ambulance crews were sent to Ness.

An RAF Nimrod was launched, along with Stornoway coastguard's helicopter and an RAF Sea King helicopter from Lossie-mouth. Searches began by a coastguard tug and the Stornoway lifeboat.

UFO watchers had a field day, with astronomers also joining in claiming there was unusual meteorite activity over the Atlantic and other parts of the globe.

Western Isles MP Calum Macdonald, now a Scottish Office Minister, tabled parliamentary questions to the then Defence Secretary, Mr Michael Portillo.

He demanded to know if the military was responsible for the incident which sparked off a major air and sea search reported to have cost more than #200,000.

Mr Portillo said there was no evidence the military was involved. The Royal Artillery Range in Benbecula confirmed they had not carried out any test firing.

A coastguard insider confirmed the extent of and effort put in to the search was very unusual. The buzz was that a missile had gone seriously wrong and was brought down by the military: ''The intensive search was not so much to discover wreckage but to ensure nothing was ever found.''

The RAF last night said the aircraft recovery section at RAF St Athan in Wales was being briefed. The trawler is expected to dock in Stornoway today.