Dyfed-Powys Police is investigating the burglary at Powys council’s Ffrwdgrech Road depot when at least 18 pieces of Stihl machinery were stolen.
Three people broke into the compound between 11pm on Sunday, June 10 and 1.30am the following morning and searched storage containers and vehicles.
At least 18 pieces of Stihl machinery were stolen when three people broke into the compound.
Cops think the raiders parked on the A40 Brecon bypass, close to the Tarell roundabout.
PC Adam Clark, of Brecon Police Station, said: "They may have been parked there for a considerable amount of time.
Anyone with information is urged to contact PC Clark at Brecon Police Station by calling 101 or independent charity Crimestoppers anonymously by calling 0800 555111 or visiting crimestoppers-uk.org.
Those who are deaf, hard of hearing or speech impaired can text the non-emergency number: 07811 311 908 and quote: DPP/0007/11/06/2018/01/C.