Police have begun to search a cemetery for the remains of a Royal Navy sailor who was thought to have been murdered in Gibraltar in 1986.
Naval rating Simon Parkes, 18, from Kingswood near Bristol, disappeared after going ashore with crewmates from HMS Illustrious.
Police said a member of the ship's crew had provided "credible" information.
The case was reopened in 2001 after a shipmate, petty officer Allan Grimson, was convicted of two murders.
Grimson has denied involvement in Mr Parkes' death.
HMS Illustrious docked in Gibraltar on 12 December 1986 during its return to Portsmouth from a deployment to Asia and Australasia.
Mr Parkes spent the evening in bars before telling friends he was leaving to buy food, police said.
The Royal Navy conducted a search when the radio operator failed to rejoin the ship, but found no trace of him.
In 2003, a number of Gibraltar cemeteries were searched after a police review concluded Mr Parkes was likely to have been murdered.
Det Insp Roger Wood said the new information made Trafalgar Cemetery "more interesting and more significant than it was in the early 2000s".
He said: "This year Hampshire Constabulary has received new information from a witness which has been assessed as credible.
"Based on that information, today we are beginning a search operation and conducting further inquiries over in Gibraltar with the hope of finally locating Simon's remains."
Mr Parkes' parents said they hoped his remains would be found and brought home.
His mother Margaret said: "We're getting older, time's getting on, we desperately need to know."
Hampshire Constabulary has issued a new appeal to trace more of Mr Parkes' crewmates, including those who were with him on the evening he vanished.