A gorse fire near Ardmore, near Londonderry raged for several hours on Friday night.
Firefighters fought the blaze, which at one stage was more than a mile wide.
It was one of 40 fires reported across Counties Londonderry and Tyrone in a single day, some of which were accidental. Others were said to have been deliberately started.
Fire Commander Kieran Doherty said: “You have to attack it from both sides, and a lot of personnel need to be deployed. We always have to be very vigilant for risk to life and property.
“If the wind changes, a fire can turn on its head very quickly.”