A large gorse fire at Cavehill Country Park, which took nearly 50 fire crew members to bring under control, was started deliberately, the NIFRS has said.
Plumes of smoke from the blaze could be seen right across Belfast, prompting warnings for households to close their windows, after the incident was reported around 4pm on Saturday.
Eight pumping appliances and a fire and rescue command support unit, along with 47 crew staff, were deployed to the scene.
A NIFRS spokesperson said that around 40 fire beaters were used to distinguish the blaze, adding the incident was brought to a close around 8.30pm.
Earlier the fire and rescue service had urged residents to keep windows and doors closed due to the large volume of smoke.
The incident on Cavehill is the latest in a number of gorse fires to take place across Northern Ireland in recent days.
Fire crews were also called to tackle a deliberate gorse fire in Newtownabbey on Saturday afternoon, with 19 personnel at the scene.
The NIFRS has appealed to the public to stay safe if they are out and about and using barbecues, and to dispose of them in the correct way.
It is also urging people to respect social distancing measures when out and about.