Thieves working under the cover of darkness stole a huge generator.
The crime happened between 4pm and 10.30pm on Sunday, December 15, after thieves cut through a chain locking gates to Frogmore Paper Mill in Fourdrinier Way, Hemel Hempstead.
Detective Sergeant Craig Flint said: “This was a large and extremely heavy item that was taken and offenders would have had to come prepared.”
Police have published pictures of the generator and the trailer it was mounted on at the website www.herts.police.uk under the latest news section.
If you can help solve the crime, phone them on 101 quoting crime reference D1/12/7446 or call Crimestoppers anonymously on 0800 555111.