Dyfed Powys Police are appealing for information after damage has been caused in Pembroke.
Between Saturday and Sunday, damage was caused to six lamps situated on the Castle Walk, Mill Pond.
The offenders have removed the inspection plates and ripped out the wiring, also damaging the glass shades.
PCSO Dave Powell said: "Whoever caused the damage were very reckless and put themselves in danger. They have been very lucky not to get electrocuted."
Anyone with information is asked to contact PCSO Powell via 101 or contact Crimestoppers on 0800 555 111