Police investigating an incident involving an air weapon in Houghton have made a further arrest.
Northumbria Police has said inquiries have established the incident happened at 10.30pm on Saturday, near to Herrington Burn.
A 15-year-old boy was injured by a pellet from an air weapon.
He remains in hospital with significant injuries.
Two 16-year-old boys have now been arrested in connection with the incident.
Detective Inspector Paul Stewart said:"This really was a nasty incident and we are doing everything we can to identify all of those involved so we can establish the circumstances of the incident and what has happened.
"Two 16-year-olds have now been arrested in connection with the incident, however, we are still keen to trace a third male - possibly the same age who may have been in the area.
"Incidents involving air weapons do not happen often but unfortunately the consequences of using them can be far reaching and as has happened in this incident they can cause serious harm."
Extra officers are in the area to speak to residents.
Acting Neighbourhood Inspector Les Goodliff said: "We know local residents may be concerned which is why we will have extra officers in the area to offer reassurance and answer any questions people may have."
Anyone with information about the incident is asked to contact Northumbria Police on 101 quoting reference 1260 190316 or Crimestoppers anonymously on 0800 555 111.