Police are seeking two men in relation to the death of Caoimhin Cassidy Crossan in a Londonderry car fire after confirming the victim was not alone in the vehicle.
Police believe the 18-year-old from Creggan was “most likely still alive when the blaze started”.
His body was found in the car in Fairview Road on Saturday, 1 June, after it had crashed into a lamp-post.
The family has appealed for witnesses to come forward.
A post-mortem examination later revealed Mr Cassidy had not been seriously injured in the crash and died after the car caught fire.
The police said the car, a Mazda 6, was stolen from a house in Oakfield Crescent earlier in the day.
“Our enquiries to date have led us to conclude that Caoimhin was not travelling alone in the vehicle and we are keen to trace the individuals who were with him,” Det Insp Michael Winters said.
Det Insp Winters added that the police had received a report of two men running away from where the vehicle came to a halt, heading in the direction of Ferndale.
Det Insp Winters also said they have been made aware of sightings of a man walking on the Buncrana Road, past the Skeoge Link Road.
He added that he was possibly injured and walking towards the Irish border.
“If you can cast your mind back and remember anything about Caoimhin’s movements, or those of the red Mazda 6, on the evening of Friday, 31 May, then please get in touch,” Det Insp Winters said.
“Any detail, no matter how small it might seem, could be invaluable.”
Police in Derry have defended their handling of a number of incidents that followed the funeral on Friday.
The teenager was buried at St Mary’s Church in Creggan.
Police believe a paramilitary-style assault and an attack on a house are linked to a car being driven erratically following the funeral.
District commander Supt Gordon McCalmont appealed to community leaders in the city to use their influence to ensure “calm” at the weekend.