By CBSBoston.com Staff

CAMBRIDGE (CBS) – Twelve firefighters were taken to hospitals in Boston with minor chemical burns after a fire in Cambridge early Wednesday morning.

They were called to an apartment building that houses MIT students on Massachusetts Avenue just before 1 a.m. and found smoke on the fourth floor and a fire inside an empty unit.

“As they started to investigate the cause and extinguish the fire they noticed an unusual odor,” Cambridge Assistant Fire Chief Thomas Cahill told reporters.

According to Cahill, when they used water to douse the flames, it reacted with chemicals that had “breached their original containers and created the initial chemical reaction.”

The 12 firefighters in the apartment ended up with what was described as “non life threatening burns to their hands when the chemicals penetrated their firefighting gear.”

In a statement via Cambridge Police, Cahill later said the chemicals were a “food grade peroxide and ammonia that combined creating the exothermic reaction.”

A team in hazardous materials suits in the apartment early Wednesday. (WBZ-TV)

Before the 12 firefighters went to the hospitals their chemical-tainted gear was laid out on the sidewalk so a decontamination team could clean it. All 12 were treated and later released.

The firefighters’ gear was laid out on the sidewalk to be decontaminated. (Photo credit: Anna Meiler – WBZ-TV)

“It was a vacant unit but it’s an occupied building other than that unit. So we’re just trying to find out who was in that unit last and where the chemicals came from,” Cahill told reporters.

No residents were hurt. Four people who were forced out of their homes. It’s not clear when they’ll be allowed back in.

CBSBoston.com Staff