The incident has resulted in St Mary’s Way being closed and buildings being evacuated as emergency services respond to the incident.
Here are photos of emergency services at the scene as the event unfolds.
1. Road closed
Police close St Mary's Way as they deal with the incident Photo: National World
2. Specialist team
Police and specialist team in Sunderland city centre Photo: National World
3. Police cordon
Part of Keel Square cordoned off as police respond to a 'malicious communication' Photo: National World
4. High Street West
Northumbria Police van enforces road closure in Sunderland city centre Photo: National World
1 / 5