A letter containing a suspicious substance sent to the constituency office of the immigration minister Caroline Nokes was not found to pose any risk, police said.

The office in Romsey, Hampshire, was evacuated on Tuesday after police received a report of a suspicious substance at the premises.

“A cordon was put in place as a precaution while tests were carried out to establish what the substance was,” the force said. “Following those tests we can confirm that the substance is not hazardous and there is no risk to the public.”

Police along with members of the ambulance and fire services, wearing full protective clothing, were seen going into the building. A police spokesperson said it was standard procedure when an unknown substance was found.

The address houses the Romsey working men’s Conservative club as well as the local MP’s office.

A Home Office spokesperson confirmed there was no alert at the department in London.

Nokes has been at the centre of the storm over the treatment of Windrush-generation Britons whose right to be in the UK has been challenged under Home Office “hostile environment” procedures requiring extensive documentation.

Nokes has been the Romsey and Southampton North MP since 2010.