A FRESH investigation could be held into the death of student David O'Halloran after it emerged he had a date-rape drug in his system when he died.

Officials at Police Scotland have confirmed they are carrying out further tests and are seeking expert opinion to find out why the teenager had high levels of GHB in his blood.

The student, from Kilmaurs, Ayrshire, a first-year Stirling University student, had been returning to campus after a night out in January when he inexplicably wandered off and vanished. CCTV footage showed the 18-year-old staggering along a street more than a mile from his halls of residence, and his disappearance sparked a search that lasted three months.

At the time police said the teenager was simply drunk and suffered hypothermia as he attempted to find his way home, but his mother, Donna, maintained her son's drinks were spiked, causing his disorientated state.

Now the results of an independent toxicology examination could point to possible foul play - after finding high levels of the date rape drug GHB in his system.

A spokeswoman for Police Scotland said: "Our inquiries are ongoing to establish where the GHB came from. Further tests are being carried out and we are not able to comment further."