Two barns in the Horsham district were broken into before Christmas.
On December 20, one in Coolham Road, Coolham, was forcefully entered.
Sussex Police say that at this time it is not known if anything has been stolen.
Two days later, a large quantity of diesel was stolen from a farm barn in Broadford Bridge, Billingshurst.
A police spokesperson said: “A large majority of the thefts that have taken place this week have been from outbuildings.
“Please ensure that you’re taking every opportunity to safeguard your property where possible with heavy duty locks, security lights and with CCTV which is time and date stamped.”