Officials say a massive six-alarm fire that ripped through a west-end high school earlier this week has disturbed asbestos inside the building, causing health and safety concerns for the workers cleaning up debris.

The fire at York Memorial Collegiate Institute broke out around 3:30 a.m. on Tuesday, hours after crews had knocked down a three-alarm fire at the same building.

At the height of the blaze, 150 firefighters were on scene. Heavy black smoke blanketed neighbourhoods, resulting in evacuations along Eglinton Avenue between Trethewey Drive and Bicknell Avenue.

By Wednesday morning, the flames had been knocked down. Heavy excavation equipment was brought in to clean up the debris and emergency crews remained on scene to deal with potential hotspots.

The cause of the fire is still under investigation, although District Chief Steve Darling said on Wednesday that officials are focusing on a boiler room in the school.

The main body of the fire was mostly contained to an auditorium. The 90-year-old building sustained extensive water and smoke damage, Darling said, and parts of the roof will need to be rebuilt.

“We talked to the engineer and he thinks most of the building can be salvaged,” he said on Wednesday. “That is an initial assessment. We are going to have engineers coming in as well afterwards to do a more comprehensive analysis of the structure of the building and the integrity.”

Officials with the Ontario Fire Marshall’s Office said that asbestos has been an issue during the investigation and the damage assessment, as there is a concern for the people working on the site.

“The building was built in the 1920s. Asbestos was used in all sorts of building materials. Now it’s been disturbed,” said Ontario Fire Marshal investigator Bryan Fischer. “It’s in a dust form and it becomes friable and it’s a huge risk to anyone working inside.”

Fischer said there is no danger to the community as there was no explosion during the fire.

“Nothing was blown into the atmosphere,” he said.

Yafet Tewelde, a community organizer, told CTV News Toronto Thursday morning that people are still in disbelief over the destruction of the historic building, which was set to celebrate its anniversary at the end of the month.

“Right now, people are still standing at the intersection just staring,” he said. “People who live in the community, and people who don’t live here anymore, or went to school here, they are all doing the same thing—standing and watching with disbelief and sadness.”

“It’s so surreal now, actually seeing the damage and destruction,” said Ed Cochrane, a former student of York Memorial C.I. “Hopefully the community, governments and the TDSB can get together and actually rebuild it or do what they can to restore the history of York Memorial.”

The Toronto District School Board said that students at York Memorial C.I. will finish the year at George Harvey Collegiate Institute, although classes are cancelled for the rest of the week in order to give teachers and staff time to prepare.