Police are trying to trace "four young men" after 100 hay bales were "deliberately" set alight in a field in Wrexham.
Emergency services were called to the scene, just off the A539, on Wednesday (August 24) at around 7pm.
A spokesperson for North Wales Fire and Rescue Service said that the hay bales were left to burn overnight under the supervision of one fire crew.
North Wales Police is now looking for four men who were seen in the area at the time.
A spokesperson for the force said: "Shortly before 7pm yesterday (Wednesday, August 24), we were called to assist colleagues from North Wales Fire and Rescue Service following a large fire in Penley, Wrexham.
"The blaze, involving a number of hay bales in a field adjacent to Madras School, just off the A539, is suspected to have been deliberately ignited.
"We are now looking to trace four young men who were seen adjacent to the hay bales prior to our arrival, and who may be able to assist with our investigation.
"We are also appealing to anybody who witnessed the incident to contact PC Tom Harrison with any information on 101, or via the website."Anyone with any information can also contact CrimeStoppers anonymously.