Emergency hazardous material crews are investigating the source of hydrogen cyanide, a dangerous chemical compound detected in the air at a Massachusetts Water Resources Authority facility in Chelsea Tuesday morning.

The Boston hazmat team responded to the MWRA plant at 340 Marginal St. in Chelsea Monday morning after the Chelsea Fire Department detected readings of cyanide in the air quality at the sewer screening facility.

MWRA spokesperson Ria Convery said that an on-site operator responded to an internal gas meter alarm at the facility on Monday night. The operator's handheld meter did not pick up hydrogen sulfide or methane, two chemical compounds that the facility's internal meters are designed to read.

"He did what he was supposed to do," Convery said. "Find anything out of the norm."

But several hours later, when the alarm system's lights were still flashing, the Chelsea Fire Department responded to the scene. Their air quality meters detected hydrogen cyanide in the air, which prompted the Boston hazmat team to investigate where the chemical compound was coming from.

Hydrogen cyanide is a very poisonous chemical compound and flammable liquid that boils when it reaches 78 degrees Fahrenheit.

A possible hazmat situation at #MWRA facility on Marginal St in #Chelsea. Readings of hydrogen cyanide detected this AM. #wbz pic.twitter.com/fZ1ua0gVf5 — Ben Parker (@radiobenparker) August 8, 2017

Spokeswoman Convery said the cyanide detection at the Chelsea facility, which runs three stories below ground, will have no impact on drinking water.

Hazmat crews are monitoring the sewage water - like the water in your toilet - is as it flows to Boston's Deer Island. Convery said crews can isolate the flow of the sewage channels once it reaches the island. She added that it is too soon to speculate where the cyanide is stemming from and whether it is in the waste flow.

Reporters on the scene say one conscious responder was taken away by ambulance on the scene.

One person being put in ambulance at #chelsea hazmat scene #wcvb pic.twitter.com/A3uzegFSRk — Katie Thompson (@KThompson_WCVB) August 8, 2017

Person just wheeled into ambulance at the #Chelsea hazmat scene. #NBCBoston — Katelyn Flint NBC10 Boston (@KFlintNBCBoston) August 8, 2017

NEW: 1 firefighter just taken to ambulance away from Chelsea MWRA facility at center of Hazmat scene. He was conscious & talking. #Boston25 — Michael Henrich (@MichaelHenrich) August 8, 2017

Hazmat crews continued to investigate scene as of 10 a.m. Tuesday morning.