CHAMPLAIN — Northern Tier firefighters quickly doused a boiler fire in the basement of St. Mary’s Academy Tuesday afternoon.

The fire began at about 3:45 p.m., when most students and faculty had already gone home for the day.

“We were lucky that it was a time of day, when most of the students had already been released, so we were very fortunate from that aspect,” said Champlain Fire Chief Chris Trombley.

Some students were still participating in after-school programs when the fire began, so firefighters simultaneously evacuated the school, sending people to St. Mary’s Church, and worked to contain the fire to the boiler.

“The main goal was to make sure the school was evacuated and isolate the fire,” Trombley said. “Once we knew we had isolated the fire to that room, we wanted to remove the smoke and prevent smoke damage.”

When the first firefighters arrived at the school, they encountered a substantial amount of smoke and high temperatures in the basement of the school, according to Trombley.

“There was a malfunction in one of the two main boilers that heat the school. This particular boiler heats the older section of St. Mary’s that was built in the early 1900s.”

Firefighters used minimal water in quickly putting out the fire, but large-diameter lines were run to the school from village hydrants in the event that more water was needed.

A fire in the early 1980s broke out in the same room of St. Mary’s Academy, and Trombley kept that in mind Tuesday.

“That (fire in the 1980s) was quite an event. So we prepared for the worst. We were lucky that we contained it to that room.”

Mutual aid was provided fire departments from Champlain, Rouses Point, Mooers and Chazy. Firefighters from Champlain were at the school until about 6 p.m.

The exact cause of Tuesday’s fire is still being investigated, but Trombley said the boiler had somehow malfunctioned.

The extent of the damage to the boiler was unknown Tuesday night, as it was impossible to perform any work on it.

“We can’t get next to it right now because it’s so hot,” Trombley said. “The school is going to move a couple classes while we look at replacing or repairing the boiler.”

Sister Marie Cordata Kelly, the principal at St. Mary’s, said school will be in session today for kindergarten through grade 6 but not for pre-K students.