Charity boxes have been taken from businesses in the city centre during clock-change burglaries.
PCSO Stephen Connolly of Preston Police is warning firms to check their CCTV systems.
He says a number of businesses within the city centre have been targeted with offenders entering via the roof or fire doors.
Electrical goods have been taken, along with whole tills, safes and charity boxes.
PCSO Connolly said: “I would advice all businesses where possible to ensure that alarms are set when building is empty, wherever possible ensure that fire doors are as secure as possible and if you’ve CCTV ensure it is fully operational and the time is correct following the clocks going back over the weekend.
“If possible I would also recommend minimising monies left on site and once closed leave tills empty and open.
“Should any key holders get a call during the night regarding alarm activation please consider reporting the incident to police on 101 before arriving.”
Anyone with information is asked to call police on 101.