BLAIR street in Bunbury was closed for half an hour after a fire took hold of the bushland on the median strip.
The fire started about 2.30pm and burnt a number of small shrubs.
Smoke from the blaze blanketed a number of nearby businesses.
The Eaton and Australind Volunteer Firefighters quickly got the blaze under control.
Eaton and Australind Fire and Rescue Service Captain Matt Stoltenbarg confirmed the fire was suspicious and said a cigarette butt may be the cause.
"Everyone must be responsible with cigarette butts and be responsible with anything at this time of year with hot temperatures that may lead to a fire," Captain Stoltenbarg said.