Lionel Rhynard, Port Williams fire chief, said the destroyed barn was believed to have been storing medical marijuana.
"We received a call for a barn on fire, a little after 10 p.m. [It’s] still under investigation but we did have reports that the building was used for medicinal marijuana grow purposes," he said.
Rhynard said the facility is licensed to grow marijuana.
On Saturday night, a fire in Scots Bay destroyed a chicken barn.
Fire crews from several departments responded.
"At its peak last night, we probably had about 50 firefighters there," he said.
"It was a difficult fire. When we arrived there was heavy fire coming through the roof of the structure."
Rhynard said no one was injured.