Ms Layman and Mr Bryers arrived at Gunluklu Bay, a resort on the Turkish Riviera just west of the popular harbour city of Fethiye, two days earlier.
Their autopsy revealed they died of an overdose and a small amount of heroin was found near their lifeless bodies, according to local Turkish reports.
Police and medics were called to the location but they could only confirm the death of the couple at the time.
An initial investigation found no scars or any indications of the cause of death and a postmortem was ordered.
Local officials said that both the bodies had been taken to the Institution of Forensic Medicine in the city of Mugla for a postmortem to be carried out.
Local Doğan News Agency reported that heroin was found in their tent and that their autopsies showed they died of an overdose.
The Fethiye public prosecutor’s office confirmed that they were carrying out an official investigation into the deaths.
Gunluklu Bay, located 12 miles west of Fethiye, has a sandy beach often photographed because of its Styrax trees, from which the bay takes its name in Turkish.
Local media reported the area is a beloved camping spot for both locals and tourists alike and is not a secluded place.
It also features some beach clubs and restaurants.
According to British Ambassador to Turkey Dominick Chilcott, almost three million British holidaymakers are expected to visit Turkey in 2018.