The constituency office of immigration minister Caroline Nokes was sealed off on Tuesday after police discovered a suspicious substance nearby.
After forensics officers investigated the incident, which occurred late on Tuesday morning at a conservative club in Romsey, Hampshire Police announced it was not hazardous and there was no risk to the public.
The scare came amid a government scandal which has seen Ms Nokes, who was not in the office at the time, come under increasing pressure over the treatment of Britain’s Windrush residents.
Earlier this week, the minister appeared to admit that some British citizens were deported to the Caribbean in error.
Interviewed by ITV News about deportations, she replied: “There have been some horrendous situations that as a minister have appalled me.”
Asked how many, she replied: “I don’t know the numbers but what I am determined to do… is say we’ll have no more of this.”
A statement by Hampshire Police on the incident in Romsey said: “We have been called to Market Place, Romsey, following the discovery of a suspicious substance.”
“Officers are currently at the scene with colleagues from Hampshire Fire and Rescue Service and South Central Ambulance Service to deal with this incident.
“An address has been evacuated as a precaution.”
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Romsey Town Council tweeted: “Due to an ongoing incident in the Market Place Romsey involving all blue light services there are roads obstructed by emergency service vehicles please avoid area for the time being.”
On Tuesday, Theresa May apologised to Caribbean leaders over the treatment of members of the Windrush generation, some of whom have lived in Britain since the 1940s.
At talks in No 10, the prime minister said she was “genuinely sorry” for the anxiety that had been caused and that she wanted to dispel the idea that the government was seeking to clamp down on citizens from the region.