A teenager was released from a vehicle following a collision, fire chiefs have confirmed.
North Wales Police announced shortly after 9pm on Friday that the A496 between Rhyd y Sarn and Blaenau Ffestiniog was closed following the incident.
A spokesman said: "Diversions are in place but try and use alternative routes."
North Wales Fire and Rescue Service said firefighters were sent to the scene along with ambulance colleagues following reports of a person being trapped within a vehicle.
The fire service confirmed on Saturday morning that two vehicles had blocked the road and crews released a 17-year-old female by removing a driver door with hydraulic equipment.
A spokesman for the Welsh Ambulance Service confirmed an emergency ambulance and a rapid response vehicle were sent to the scene.
One patient was conveyed to Ysbyty Gwynedd, the spokesman said.
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