Nanaimo Fire Rescue rushed to extinguish a small grass fire along the E&N Trail near Wellington Road and the Island Highway at 7 p.m. Sunday.
Rick Kwasnecha, fire investigator, said passing motorists reported the fire, which was believed to be set intentionally.
"It was not an accidental fire," said Kwasnecha, adding the incident was passed to the Mounties for investigation.
He added after Saturday's heavy rainfall, it was unlikely a carelessly discarded cigarette butt or other unintentional act could have sparked the fire.
There were no injuries and damage was limited to a small area of grass.