A woman is in a "serious condition" in hospital following a crash on the Letterkenny Road in Derry city on Tuesday morning.
The Letterkenny Road has been shut in both directions.
Motorists are being asked to avoid the area.
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A spokesperson for the PSNI said: "Police are appealing for information following a single vehicle road traffic collision in Derry / Londonderry."
PSNI Craig said: "We received a report shortly before 8.45am this morning, Tuesday 11th July, that a silver Peugeot 207 had been involved in a collision with a tree on the Letterkenny Road.
"Officers attended, alongside colleagues from the Northern Ireland Fire and Rescue Service and Northern Ireland Ambulance Service.
"One woman was taken to hospital where she remains in a serious condition at this time.
“The Letterkenny Road remains closed at this time."
Inspector Craig added: “We are appealing to anyone who was travelling in the area around this time and date and who has dash-cam footage, to contact police on 101, and quote reference number 345 of 11/07/23."
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