A 53-yr-old man is in a life threatening condition after being stabbed in Plains Farm on Monday.
Police were called to an address in Purley Road at 4:20am, where the man had suffered a serious stab wound to the leg.
He has been taken to Sunderland Royal Hospital where his injuries are described as being life threatening.
Four people have been arrested in connection with the incident, and police are appealing for anyone with information to come forward.
Superintendent Jim Napier, from Sunderland Area Command, said: “We have extra officers in the area to offer reassurance to residents. I’d ask anyone with concerns to speak to them.
“Detectives are continuing to investigate the incident. We would urge anyone with information or any witnesses to come forward as their information could be vital to assist with enquiries.”