Weston Favell Shopping Centre was evacuated this morning (Tuesday).
Staff were reportedly evacuated from the building at around 8.15am, according to a shop worker.
An eyewitness told the Chron that shoppers and delivery drivers were queuing outside to get in.
A spokesman for Weston Favell Shopping Centre said: "I can't say anything at the moment."
Northamptonshire Police were uable to provide any further information at this time.
It is believed the shopping centre has now reopened.