Emergency services were called out last night to a fire at Silloth Airfield.
Six appliances attended the blaze, in addition to a specialist water bowser from Penrith.
The fire is in a former aircraft hanger at the airfield.
Fire officers said there appeared to be a large quantity of smoldering plastic. They said there is 800 tonnes of the plastic inside the hanger, but not all of it is alight.
Fire crews will be staying at the airfield throughout the night.
Fire fighters will resume in the morning.
The cause of the fire is currently not known. Three appliances will stay overnight and work will resume at first light.
Ian Seel, from Cumbria Fire and Rescue said: "If people live locally they should keep doors and windows closed. It is low risk to the public."
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