Seven people have now been arrested in relation to an incident where a man was knocked down, leaving him in a critical condition.
At around 9.40pm on Friday police received a report that a 42-year-old man has been hit by a vehicle on Seaham Road in Houghton.
The vehicle was believed to be in convoy with a second vehicle, both left the scene leaving the man seriously injured in the road.
He was taken to hospital where he remains in a critical and life-threatening condition.
Detectives are carrying out inquiries and appealing for any witnesses, in particular they would like to speak to anyone who saw the two vehicles - a white Seat and silver Golf and their occupants.
Seven people have now been arrested, the latest, a 17-year-old boy is in custody this afternoon.
Two men – aged 19 and 38 - remain in police custody.
Three others - two men aged 29 and 37 and a 37-year-old woman - have been released under investigation and a 35-year-old man has been released with no further action.
In the aftermath of the collision, police say they believed another incident which happened on the same night in Houghton was linked to it.
At around 11.25pm, officers received a report of a disturbance at an address in Queensway.
They found three men had entered a home and assaulted a man before running off.
Detective Chief Inspector Lisa Theaker said: "This was a serious incident that has left a 42-year-old man in hospital in a critical and life-threatening condition, it is important we find out what happened so those responsible can be dealt with.
"We are keen to speak to members of public in the area at the time of the collision.
"In particular if anyone saw the vehicles or occupants in the area either before or after the incident we would like them to come forward and speak to us."
Any witnesses should ring Northumbria Police on 101 quoting reference 1159 020617 or Crimestoppers anonymously on 0800 555 111.