BRAINTREE, MASS. (WHDH) - A chemical spill prompted a massive hazmat response and the evacuation of the Harvard Vanguard Medical Associates building in Braintree on Wednesday afternoon.

Emergency crews responding to the building on Grossman Drive shortly after 12 p.m. escorted dozens of people out to a group of awaiting ambulances in the parking lot.

Many people were complaining of nausea and headaches following an acid spill in a surgical unit.

“I believe they said it was approximately four ounces or so of a chemical called phenol and it’s used for surgical injection,” a worker told 7NEWS. “It was in a vile form and it was dropped.”

Twenty-one people, including a firefighter, were treated at the scene. Seven employees suffering from respiratory issues were taken to an area hospital as a precaution.

Crews cleaned up the spill and brought it to the basement of the building but the fumes had already spread through the air.

The building was still being ventilated as of late Wednesday afternoon.

It’s not clear when it will be reopened.

This is a developing news story; stay with 7NEWS for updates online and on-air.

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