A hazardous material response team with the Boston Fire Department was deployed in Cambridge on Wednesday morning, where 12 firefighters were taken to the hospital with chemical burns.
Firefighters responded to a call for the smell of smoke in a corner apartment on the fourth floor of 355 Mass Avenue, near the edge of the Massachusetts Institute of Technology campus and Kendall Square. But when they arrived on scene, they noticed an unusual smell.
"There were no difficulties fighting the fire. The difficulty was identifying the chemicals," Cambridge Assistant Fire Chief Thomas Cahill Jr. said.
The firefighters suffered minor burns to their hands by a combination of cleaning products -- food grade peroxide and ammonia, which aren't normally mixed. They have since been released from the hospital and are expected to recover.
The five-story apartment building houses about 45 female students from MIT during the school year, but anyone can live there during the summer. The 10 residents evacuated the building, which is run by the MIT group Women's Independent Living, and was reopened by mid-morning.
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It is unclear how the chemicals ended up mixing and why they were in the unit, since it is vacant.
"At this point we're just trying to find out who occupied the building. It was a vacant unit but it's an occupied building other than that unit," Cahill Jr. said. "So we're just trying to find out who was in that unit last and where the chemicals came from."
Massachusetts Avenue and Brookline and Landsdowne streets were closed for the investigation, the Cambridge Fire Department wrote on Twitter. No further information was immediately available.