Devon and Cornwall Police think the fire may have been started deliberately.
Detectives are appealing for anyone who may have seen any suspicious activity in the area either in the late evening of Sunday 12th May or the early hours of Monday 13th May.
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Heavy showers overnight, hail and thunder possible, humid
Heavy showers overnight, humid, thunder possible
The Maltings shopping centre was closed to the public after a small amount of the Novichok substance was found in the area.