A man was taken to hospital with life-threatening injuries after he was found lying on a road in Berwick.
Emergency services found the injured man on North Road at 2am on Sunday.
The 39-year-old had been left seriously injured on the northbound carriageway close to the junction with Crispin Road.
It is not currently known how the man's injuries were caused.
He was taken to the Royal Victoria Infirmary in Newcastle where he is described as being in a critical but stable condition.
Police officers are now keen to speak to a man and woman who were believed to be at the scene and were seen to get out of a taxi.
The woman assisted the injured man before she and the other man got back in the taxi and left.
Police are also keen to trace a woman who found a mobile phone near to the Toll House and handed it to another woman.
Officers are also hoping to speak to any drivers who were in the area at the time and may have dashcam footage of the incident.
Anyone with information is asked to get in touch with Northumbria Police by calling 101 quoting log number 234 090220.
