BOSTON -- A chemical scare led to an hours-long standoff and arrest in Boston's posh Beacon Hill neighborhood overnight.

Police said a woman who barricaded herself in her apartment with chemicals was taken into custody early Wednesday in connection with the six-hour ordeal.

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The incident unfolded in the area of Temple and Cambridge streets near the Massachusetts Statehouse before 9 p.m. They were called on a strange odor at 21 Temple St.

Authorities evacuated the Beacon Hill building and hazardous materials crews responded. They said a woman spilled or poured chemicals in her apartment, which reeked of ammonia.

"We didn't have any confirmed reports on that. We didn't know exactly what chemicals, if any, she might have been mixing, so we erred on the side of safety," a Boston fire official at the scene said.

Officials called for a second-level hazardous materials response, meaning that firefighters inside the building must use air masks.

Residents said the woman was a former MIT chemist who lived in the unit. She allegedly kept police at bay for five hours before police were able to get her to surrender.

"She resisted somewhat with the officer. She was taken into custody and brought down, and then she was decontaminated downstairs and then she was decontaminated a second time and she's on her way to the hospital," a police officer at the scene said.

Police did not immediately release the woman's name.

Hazardous materials specialist Fred Ellis would not say what exactly was spilled, but said it was a household chemical.

"She was a woman who was on meds and just missed a few of her normal doses and she just lost reality," Ellis said.