Police are urging businesses and contractors to be alert to theft after a number of items of plant were stolen from sites in the isles.
Incidents have been reported in Scalloway, Tingwall and Bixter in recent weeks, all involving items of industrial plant being removed from construction sites.
Enquiries are ongoing and officers are keeping an open mind about any links between them.
Inspector Martyn Brill said: “We are urging anyone working with potentially valuable equipment to be security conscious given these recent incidents.
“Please make sure that property and equipment is secured as thoroughly as possible and do not leave valuable items unattended and in plain sight, particularly if it is to be left in a remote area.
“It is worth considering security cameras or lights which act as a relatively simple deterrent against thieves.
“I would also ask businesses who may have had equipment stolen or who may have concerns about suspicious activity around their sites to report issues to police as soon as possible to allow officers to take the appropriate action.
“Nothing is entirely foolproof but it is worth taking a few simple steps to deny would-be thieves an opportunity.”