Students at Armstrong High School in Plymouth resumed classes Thursday after an unexpected sewage backup caused partly by vape pens forced school officials to cancel classes Wednesday.

Wednesday would have marked the first day of school for students in grades 10 through 12.

“I know this was a disappointing way to begin the school year,” Principal Erick Norby said in a message posted on the school’s website. “I’m thankful for our custodial and nutrition services teams, who partnered with a professional cleaning crew to remedy the situation.”

The cause of the backup was a combination of non-flushable items, including wet wipes, vape pens and paper towels, school officials said.

Plumbing issues have been fixed and staff have sanitized the kitchen, dish room, bathrooms, and other areas, officials said.