Two men were taken to hospital following a head-on crash on the A470 near Trawsfynydd.
A white Ford Transit tipper collided with a grey Toyota Aygo at the junction with the A4212 shortly before 6.45am on Wednesday morning.
One of the drivers was taken by ambulance to a specialist trauma unit at the Royal Stoke University Hospital with serious injuries.
The second driver, who suffered minor injuries, was taken to Ysbyty Gwynedd in Bangor.
The road was closed for around three hours after the crash before reopening.
Sergeant Gerallt Williams from North Wales Police said: "I’d appeal to anybody who may have been travelling around the area yesterday morning and who may have witnessed the collision or who saw either vehicle just prior to the collision to please contact us."
Anyone with information should contact the Roads Poicing Unit on 101 or use the live web chat, quoting reference no. O180227.
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