A small chemical explosion in an Erie Community College South classroom Monday morning left three people with minor injuries and forced the closing of the building for the rest of the day, authorities reported.

The explosion occurred at about 9:30 a.m., as part of a classroom experiment in Building 3 of the ECC South campus. Two students and an instructor were treated at the scene for burns that were described as minor, Town of Hamburg police said.

School officials closed Building 3 as a precaution for the rest of the day, but the rest of the South Campus ran a normal schedule. Building 3 was expected to reopen Tuesday.

ECC said the mishap resulted from a minor chemical spill and an unexpected reaction.

“We’re calling it an explosive reaction,” ECC public information officer Michael Farrell said, before relaying an explanation from chemistry instructors. “Potassium was mixed with ice, which in turn produced potassium hydroxide. When this mixes with oxygen in the air, it creates heat, which would induce an explosive reaction.”

No damage was reported to the building.

Six agencies, including emergency services personnel and a haz-mat team, responded to the explosion.

“Luckily, it was a minor incident, but it created great training for the agencies involved,” Town of Hamburg police Lt. Jim Koch said.