People living in the Seacoast Road area of Magilligan are being urged by police to watch out for suspicious activity close to the Rivers Agency site.
Inspector Jenny Hudson said that in recent weeks several incidents of theft and criminal damage had occurred.
“In the most recent, on Tuesday night (2nd) diesel was stolen from a machine on the site. We believe a vehicle was used by the thieves.
“We would ask anyone living nearby to make a note of any vehicles they see close to the site at unusual times, such as at night and the weekends and then give information to police.”
Information can be given on the police non-emergency number, 101, or by calling the Crimestoppers Charity anonymously on 0800 555 111.