A fire burned through 30ha of bushland near the Yongah Hill Immigration Detention Centre in Northam last night.
It was one of five fires in the greater Northam area yesterday which authorities suspect were deliberately lit.
The blaze started about 5pm near the intersection of Great Eastern Highway and Mitchell Avenue, opposite the detention centre.
No asylum seekers had to be evacuated.
Firefighters were kept busy into the night as scrub fires threatened homes near Great Eastern Highway and Mitchell Avenue.
Roads were closed and people were urged to evacuate or prepare to defend their homes, before crews brought the situation under control.
A Department of Fire and Emergency Services spokesman said crews would continue to closely monitor the area today.