Speaking to the BBC, Emma Thompson, who works close to the cordon, said: “We’ve seen armed police with what looks like a riot shield, the incident is in the middle of Queen Street… it’s been going on for quite some time.”
Nottinghamshire Fire and Rescue Service said it sent two engines from Newark and Highfields fire station to the scene.
A Nottinghamshire Police spokesperson said: “Officers are currently in attendance at Queen Street, Southwell, following a concern for safety report at 11:52 GMT.
“The street remains closed as officers deal with the incident.
“This is an isolated incident with no wider risk to the public.”
The Minster School in Southwell sent out an email to parents just after 13:00.
It read: “We are currently not in a lockdown situation, although we understand some primary schools in the local area are.”