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 family of Christian Pay, who died on Friday after suspected substance abuse at a festival, have paid tribute to the Millom teenager.
The Borders Railway is to be officially opened by the Queen... on the day she becomes Britain's longest serving monarch.
Christian Pay's family say he was "loved by all" and had "the heart of a lion". The 18-year-old died after falling ill at the festival.