UFO investigators are now calling for more witnesses to come forward after the shock report was made to a specialist organisation.

The UFO sighting allegedly happened last Tuesday in the Gulf of Mexico about 80 miles southeast of New Orleans, and reported two days later.

The report was made to the US-based National UFO Reporting Center (NUFORC), which keeps a database of sightings and investigates cases.

One unnamed crew member, who was the chief engineer of the OSV, said the UFO was five times bugger than the 240 feet oil rig supply ship they were on.

The report said: "At close to 7pm on March 21, just before dusk, myself and four of the crew members aboard our vessel saw a craft that appeared to be five times our 240 feet vessel in length.