LISBON — Officials abruptly canceled school Monday after discovering someone had let the air out of 23 bus tires, hitting all but one bus in the fleet.

Heather Wilmot, the director of student services, said a bus driver arriving for his regular morning route found the flat tires and alerted the maintenance director. The buses were parked on Capital Avenue next to Public Works.

"We really don't have any details on who or when (it happened). That's part of the investigation right now with our Police Department," she said.

In total, 23 tires were deflated on 15 buses. A majority were front tires. None were slashed and no other damage was found.

After the tires were inflated — some had to be remounted — Wilmot said the school opted to send the buses to Don's Automotive for an overall safety check. The work took most of the day.

She canceled classes in the morning using the school's "Alert Now" system, similar to a phone alert used during snow days.

She used that same system late Monday afternoon to send parents a second message "giving them the information that we know about the event, but also letting them know our buses are safe and operational and also prepared to transport students tomorrow."

It's not anything the district has experienced before.

"Hopefully not ever again," Wilmot said. "It is something we intend to take seriously."

kskelton@sunjournal.com