The public got a first look Thursday at the extent of the damage to Carmel High School caused by a mechanical-room explosion.

The Carmel Fire Department posted photos on Facebook showing extensive damage to a portion of the massive school's roof and rubble filling stairwells and part of a gym.

"We wanted to share these photos for people to understand the magnitude of the incident," the department said in its post. "And how fortunate we are this wasn't worse."

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On Wednesday the department said the explosion came from a second-floor mechanical room, injuring two people and starting a small fire on the roof. Department spokesperson Tim Griffin said Thursday fire officials believe it was some sort of gas explosion that occurred during maintenance to a boiler.

The Indiana Department of Homeland Security said Thursday that there was no boiler malfunction. Workers were doing routine service and a "natural gas leak occurred, leading to an explosion during the reigniting process."

The district was replacing a gas line while students were on winter break, Superintendent Michael Beresford said during a news conference Thursday. At the same news conference, Griffin said there was no evidence of foul play.

Fire department officials did not give a damage estimate. Department spokesperson Michael McNeely told IndyStar that such an estimate is difficult to approximate for a commercial building, but that the school may be looking at "hundreds of thousands" of dollars in damage.

School officials did not immediately respond to IndyStar's questions about the dollar amount of the damage.

A Carmel High School maintenance employee and a contractor were taken to Eskenazi Hospital in Indianapolis, one with severe burns. The fire department did not offer an update on their condition in the Thursday post, citing patient privacy.

Beresford tweeted Thursday morning that he spoke to the two victims, who officials said were conscious when they were taken to the hospital.

"I spoke with the two men that walked out of an explosion and fire last night - miracles happen!" he wrote.

Beresford estimated that about 100 people were in the building at the time of the explosion. Students were taken to the locker rooms where they could be picked up by parents. No students were injured.

"We're just most thankful that everybody is safe," he said Thursday.

Wednesday night, fire officials said they were evaluating the structural integrity of a nearby entrance, as well as the stairwell and surrounding area involved. The investigation continued Thursday.

All activities at the school Thursday were cancelled. Students are currently on winter break and are scheduled to return Jan. 8. Beresford told reporters it is too soon to say if repairs will be finished in time. He said multiple times, "There's a lot of work to get done."

Contact IndyStar reporter Emma Kate Fittes at 317-513-7854 or efittes@gannett.com. Follow her on Facebook and Twitter: @IndyEmmaKate

