Eleven fire crews in all were called to tackle the fires at Talsarnau and Maentwrog in Gwynedd.
The blaze at Talsarnau which spread to a nearby nature reserve was brought under control after six hours.
The second blaze, at Tan y Bwlch in Maentwrog, reignited several times over the weekend and again on Monday.
The blaze torched 50 acres (20.23 hectares) of gorse and a fire crew was damping down equipment to control the fire.
This first fire at the site was started by a spark from a steam train, the fire service said.
Smoking materials
Six different fire crews from across the region were called to fight this gorse fire.
Firefighters from Harlech, Blaenau Ffestiniog, Llanrwst and Pwllheli attended the Talsarnau blaze on Sunday which spread to the Countryside Council for Wales' nature reserve near Llyn Traws.
The fire service said on Monday the fire is thought to have been started accidentally by smoking materials.
On Saturday firefighters attended a blaze in a barn in Denbighshire which involved around 100 tonnes of hay and straw.
It took five hours for officers from Rhyl, St Asaph and Prestatyn along with the Shower Unit from Colwyn Bay and the Environmental Protection Unit from Wrexham to bring the fire under control.
The road was closed for a time while crews fought the fire and damped down adjacent buildings.
The cause is under investigation
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