The chair of the Nanaimo-Ladysmith school board says squatter activists who occupied a closed school for 18 hours over the weekend left behind a mess that will cost the district at least $100,000 to clean up and repair.

Steve Rae posted photos of the damage to Rutherford Elementary in Nanaimo, B.C., on social media.

A large amount of drug paraphernalia and harm reduction supplies were left behind by the squatters. (Steve Rae)

"I was mortified. They destroyed all the doors on the bottom floor. They cut holes in the roof to hang their signs on," said Rae.

"But the most troubling part for me was the amount of drugs we found in there. There were cases of needles, there were naloxone kits all over the place."

The group, which includes members of the Alliance Against Displacement, broke into the school on Friday, claiming the action to be in opposition to "anti-homeless hate" related to a Sept. 21 B.C. Supreme Court injunction ordering people out of the Nanaimo DisconTent City homeless encampment.

A hallway barricade in Rutherford Elementary School. (Steve Rae)

The RCMP emergency response team moved in and arrested approximately 20 protesters on Saturday.

On Twitter the group claimed the school was already a mess, with "textbooks, school supplies and trash ... strewn everywhere when we entered."

It also claimed the RCMP was responsible for the damage shown in the photos, a statement Rae calls "absolutely ridiculous."

A full syringe sits on the ledge of a classroom whiteboard. (Steve Rae)

"I walked into the building with the RCMP as soon as it was safe and it was a complete and total disaster," he said.

"We acknowledge clearly that there is a homeless issue in Nanaimo and in the province of British Columbia and we have extreme empathy for it, but this is not the way to go about helping your cause."

Rae said the school district is now hiring outside security at two other schools that the group has threatened to occupy.

"This comes at a significant cost," he said. "And we're going to have to take that from money earmarked for kids' classrooms."

Rutherford Elementary closed down in June due to the opening of a new school annex nearby.

Some of the drug paraphernalia and harm reduction supplies left behind by the squatters. (Steve Rae)

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