Emergency services dealt with several incidents on a Carlisle commercial estate – including two arsons.
Police are appealing for witnesses who were in the area of Viaduct Estate Road around 4.30pm on Monday.
Eight properties were damaged, including windows and doors smashed.
Firefighters from Carlisle West and Carlisle East stations attended to tackle the blazes.
A police spokesman said: “One fire took hold and caused significant damage.”
Anybody who may have information or has seen anything or anyone suspicious in the area at the time is asked to contact officers.
Anyone with information can report online at www.cumbria.police.uk/reportit, quoting incident 148 of January 3 or call 101.
Alternatively, contact Crimestoppers anonymously on 0800 555 111.
