Twelve people were evacuated from a South End apartment building and four Boston police officers and an ambulance crew were taken to a hospital after a woman committed suicide Monday night inside an apartment by ingesting a toxic chemical, fire officials said.

Boston Deputy Fire Chief Steve Dunbar said at the hazmat scene that the woman ingested the chemical on the first floor of 676 Mass. Ave. at about 9 p.m. and was later pronounced dead at Boston Medical Center.

He said four police officers and the ambulance team of two EMS workers were being quarantined at BMC to determine whether they were affected by the substance.

Dunbar said a relative of the woman, whose name and age he did not know, reported that the victim told her she ingested a chemical and asked that her cats be taken care of.

The deputy fire chief said the victim appeared to be young, but he could not be more specific.

He said the woman is believed to have ingested sodium azide, a chemical used to make airbags. “But it can metabolize into some kind of cyanide,” Dunbar said, adding that the woman died about an hour or two after ingesting the substance.

He said at about 12:20 a.m. Tuesday that crews were preparing to reenter the apartment building to see if it presented a safety risk, a process expected to take a few hours.

Dunbar also said the officers and EMS workers who were quarantined did not appear to be showing signs of being adversely affected by the chemical.