More than 100 screws have been found scattered on a slip road next to the A40 in Carmarthenshire in what police are describing as a "deliberate act".
The screws were found in the overspill entrance to the Nantyci Showground on the dual carriageway near Carmarthen on Thursday, February 8.
Police believe the screws were placed in the slip road to target police enforcement vehicles and have appealed for anyone with information to contact them.
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A spokesman for Dyfed-Powys Police said: "This is the second time in as many weeks and believed to be a deliberate act to damage police enforcement vehicles.
"Anyone with information that could help officers with their investigation is asked to report it."
Those with information about the incident are asked to contact Dyfed-Powys Police on 101, by emailing 101@dyfed-powys.police.uk or calling Crimestoppers anonymously on 0800 555 111.
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