Police were called to a robbery at a building society in Rothwell at about 9.10pm yesterday evening (Monday, June 3).
Two security guards were injured following the incident at the Nationwide on Bridge Street in the town. The guards were taken to hospital following the assault, where their condition is not believed to be serious.
Police have appealed for help tracing a grey or silver Audi, which was seen driving away from the scene at high speed.
A force spokesman said the thieves had escaped with an undisclosed amount of cash.
Eyewitnesses said the street was completely sealed off by police between the Post Office and the roundabout which forms the junction with Desborough Road.
A G4S security van was also taped off, while an ambulance was called to the scene.
The building society has been targeted a number of times in the past. In November last year, a substantial amount of cash was taken by two thieves who forced their way into the premises during the evening.
In August 2011, it suffered a ram raid, with a gang smashing the front of the building, leaving its cashpoint lying in the street.
And in July 2008, there was another armed robbery at the building society.
Anyone with any information is asked to call Northamptonshire Police on 101, or give information anonymously to Crimestoppers on 08000 555 111.