A 17-year-old boy is in hospital with serious injuries after a crash on the A465 Heads of the Valleys road.
Emergency services were called at around 3pm on Thursday, September 24 to reports of a serious crash between Hirwaun and the former Baverstock's Hotel.
The crash involved a white Renault Clio and a bronze Toyota Landcruiser.
A statement from South Wales Police said that as a result of the crash, the 17-year-old driver of the Clio, who is from the Merthyr Tydfil area, suffered "serious and potentially life-changing injuries".
He is currently being cared for at the University Hospital of Wales in Cardiff.
The 57-year-old male driver of the Toyota was taken to Prince Charles Hospital in Merthyr as a precaution.
The road was closed for more than six hours as police carried out investigations at the scene.
A spokesman added "Officers would also like to hear from anyone who saw either vehicle being driven in the run up to the collision, or who may have any other information regarding this matter.
"The A465 at the location remained closed for several hours to allow for vital investigative work to be completed. Officers would like to thank the community for their patience and understanding during the disruption caused by this."
Police are appealing for anyone who witnessed the collision, or have relevant dash-cam footage, to contact them via 101 quoting reference *350101.
