A man armed with a knife is believed to be holding several members of staff at a job centre.
Specialist negotiators are at the scene at the Jobcentre Plus in Clifford Street in the Byker area of Newcastle after being called at 8am on Friday.
Nearby accommodation has been evacuated, while the metro station is closed.
In a statement, Northumbria Police said: "Officers have attended and found a man armed with a knife had entered the premises and it is believed that several members of staff are being held there. Several other staff members have left."
Police said it is believed the man involved is known to the job centre, adding that it is being treated as "an isolated incident" and there are no reports of any injuries.
Roads around the building have been closed and no trains are passing through Byker while officers deal with the "ongoing situation".
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