Sainsbury's supermarket on Sidney Street has been shut down today and cordoned off by police.
At around 3.30pm today, shoppers who were in the supermarket were startled when an alarm started to buzz continuously.
Speaking to The Cambridge Student, an eyewitness and third year Girtonian said: "Staff began to herd everyone towards the doors. A few minutes later, a staff-member later came out and claimed there was a gas leak, and they would be shut for the next hour. Some people left but mostly everyone milled around outside."
Whether the incident was a gas leak is currently unconfirmed.
Area cordoned off – Credit: Colm Murphy
Two police cars and a fire truck later arrived at the scene and cordoned off the area.
When The Cambridge Student asked officers at the scene what had happened, officers were only willing to say there had been an "incident". They reassured passers-by that this was "nothing to worry about". One officer said there would "probably be a press release later". Perhaps then the mystery will be solved.