The giant Canadian flag hanging in front of Kitchener's TheMuseum may have to come down after it was smeared with a black substance in an apparent act of vandalism.

It appears to have been spilled over the flag from the building's rooftop. A banner had also been draped across the top of the maple leaf, which read "150-plus years of resistance, unsettling 150."

"I'm not sure if it's actual paint or what it is we're dealing with, CEO David Marksell told CBC News on Monday. "I can actually see out my window — the black streaks."

The banner has since been taken down, and TheMuseum is now seeing if the flag can be scrubbed clean.

He said the flag is made of mesh, and hopes it can be power washed clean. If not, it would have to be removed and possibly replaced.

Marskell said the banner will be added to TheMuseum's current exhibition "A Cause for Celebration? First Things First."

The exhibition features three indigenous artists and reflects on how First Nations have been treated over the past 150 years.

"I do not like what happened, but I'm glad that TheMuseum is looked at as a place for ideas and dialogue and communication," said Marskell.