Six packets of building insulation were stolen from a compound in Northampton.
The compound in Greenwood Road, St James, was broken into sometime between 12.10am and 12.30am on Monday, April 6.
Two white men wearing hoodies were seen to take the packs of Kingspan insulation.
Witnesses, or anyone who knows anything about this incident, can call Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111 or use the anonymous online form at www.crimestoppers-uk.org