Burglars removed roof tiles to get in and search a business before escaping through a fire door.
They broke into Sarrington House in High Street, Corby, sometime between 1.30am and 6am on Monday, November 23.
They got into the building through the loft after removing some roof tiles.
A police spokesman said: “They searched a number of offices before making their escape through a fire door.”
Witnesses, or anyone with information about the break-in, is asked to call Northamptonshire Police on 101 or they can call the independent charity Crimestoppers anonymously on 0800 555111 or use the anonymous online form at www.crimestoppers-uk.org.