Firefighters suspect a huge at a tyres depot was started deliberately.
Crews tackling the fire in County Londonderry, which involved up to 50,000 burning tyres, found four separate fires across the one-acre site, according to news reports.
The inferno broke out at Campsie Industrial Estate in Eglinton last night and it is believed it could take until midday tomorrow to fully extinguish.
The Fire Service is examining whether the blaze was started deliberately.
Police have appealed for information and local residents have been warned to keep their windows closed as the fire sent a huge plume of smoke into the air.
Fire Service District Commander Ian Doyle said that 16 appliances have been pumping thousands of gallons of water onto the fire.
Colleagues from neighbouring County Donegal were also brought in to help with the effort, as firefighters worked through the night to bring the blaze under control.
Alex Kapadia, Operations Team