Firefighters say at least three dump trucks were fully engulfed in flames when they arrived.
The fire was located at the back of a large compound on the company's lot and firefighters had to force the gate open to gain access.
Further complicating firefighting efforts was the location of the closest hydrant, which was some distance away on on River Road.
The fire has been deemed "suspicious" by the fire department. Investigators have been called in to determine the cause.
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