Detectives investigating the fatal road traffic collision in Derry on Saturday June 1st are making a number of specific appeals for information.
The body of 18 year old Caoimhin Cassidy was found inside a red Mazda 6 which crashed on the Fairview Road in the early hours of June 1st.
Results from a post mortem have revealed that Caoimhin was not seriously injured as a result of a crash, and was most likely still alive when the blaze started.
Detective Inspector Michael Winters says enquiries to date have led them to conclude that the 18 year old was not travelling alone in the vehicle.
Police are keen to trace the individuals who they believe were with him.
Anyone who can identify two males reported to have been seen running from where the vehicle came to a final halt on Fairview Road, near Knockalla Park, heading in the direction of Ferndale is being asked to contact the PSNI.
Detective Inspector Winters says they've also been made aware of sightings of a male, possibly injured, walking on the Buncrana Road, past the Skeoge Link Road, towards the border a short time later.
Anyone who can remember anything about Caoimhin's movements, or those of the red Mazda 6, on the evening of Friday May 31st are asked to come forward.