Nearly 150 firefighters are battling a blaze which broke out this afternoon in São Marcos da Serra, Silves.
The fire started at around 3.43pm in a valley in the hills near the small village.
Firefighters are being aided by 43 vehicles and five aircraft.
So far, the flames are not reported to be threatening any houses or the nearby railway track.
São Marcos da Serra was ravaged last summer by a fire which destroyed the house of a local couple.