Detectives are investigating following a deliberate blaze at an electricity sub-station in Kilmarnock.
Police discovered the fire while on patrol on Knockinlaw Mount in the Onthank area around 10.40pm on Monday.
Fire crews and the utilities company were called and residents nearby were evacuated.
The area was cordoned off while investigations were carried out and police say the fire was set deliberately.
Detective sergeant Jamie Carruth of Kilmarnock Police Station said: “Following initial enquiries, the fire is being treated as wilful and an investigation is ongoing.
“I would appeal to anyone who was in the area on Monday evening between 10pm and 10.40pm who witnessed anything suspicious. We are also keen to obtain any dashcam from motorists driving in this area between those times, or anyone with personal footage.
“There are increased police patrols in the area to provide public reassurance and anyone with concerns should speak to officers.
“I would urge anyone with information on this crime to contact 101 with reference 3630 of November 21. Alternatively Crimestoppers can be contacted on 0800 555111, where anonymity can be maintained.”