A Dumfries and Galloway Police spokesman said:
“The causes of the fires are being investigated. We are anxious for anyone with information to come forward so that whoever is responsible can be apprehended.”
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The driver of a Rangers supporters' bus which crashed on a roundabout killing a fan blamed the brakes when he was interviewed by police.
Sandy Murray, of Police Scotland, was was giving evidence at the trial of a bus driver who denies killing Ryan Baird by dangerous driving.
34-year-old Christopher Peck was involved in a head-on crash with a drunk driver. His funeral has taken place in his hometown, Workington.