Bryan was found unresponsive beside the L3050 at Cottage Cross, near Clonlara, on Friday after an incident involving his scrambler bike.
The teenager was pronounced dead at the scene.
Gardaí are now trying to establish the movements of a Skoda Octavia which was travelling in the Clonlara area of Co Clare and Castleconnell in Co Limerick.
Investigators want to speak with the driver or anyone else who was travelling in the vehicle between 6pm on Friday and 11am on Saturday, as they may have information that could assist the investigation.
A second vehicle is also believed to have been involved in the incident and did not remain at the scene.
Gardaí are appealing to anyone who was driving through Clonlara, Castleconnell or the surrounding areas during the relevant period to come forward.
They are particularly interested in hearing from motorists who may have captured the Skoda or other relevant activity on dashcam or other camera footage.
Anyone with information is asked to contact Henry Garda Station on 061 212400.
Information can also be provided through the Garda Confidential Line on 1800 666 111 or by contacting any Garda station.
Gardaí continue to investigate the circumstances surrounding Bryan's death.
