A person is in custody after an incident involving armed police in the South Canterbury town of Waimate.

A police spokesperson says lockdowns placed on two schools have been lifted and cordons have been stood down.

A police spokesperson said an area of the town was cordoned off as a precaution.

A witness, who does not want to be named, said a perimeter of about three or four streets were cordoned off.

"I'd say there are at least eight [police] cars and they were all armed. They didn't look like AOS but they were certainly armed.

"It is a bit unexpected to see armed police in Waimate."

A post on Facebook by Waimate Main School said they were in lockdown at 2.30pm.

"There is a heavy police presence close to the school and the police have advised that there is no threat so please remain calm.

"Please do not come onto the school site until we inform you that the lockdown is lifted," it said.