Firefighters worked through the night to bring a blaze at a recycling plant in Hartlepool under control.
More than 50 firefighters tacked the incident at Cleveland Waste Paper, in Mainsforth Terrace, which started on Thursday evening.
No-one was hurt but people in nearby properties were told to be aware of drifting smoke from the fire.
A joint police and fire service investigation into the cause of the blaze is under way.
Cleveland Fire and Rescue Service watch manager Anthony Mosely said: "The site owners had told us that the main danger was a storage area containing gas oil. But we were able to make the area safe quickly.
"It did take us a while to get the fire under control because of the limits of water supply in the area.
"We are likely to be here for some time damping down."
Cleveland Waste Paper handles hundred of tonnes of material a year from commercial premises.
It also has sites in Middlesbrough, Stockton, Redcar and Darlington.