A plume of toxic gas flared over Amityville Village when a chemical reaction went wrong at a soap factory late Tuesday afternoon, authorities said.

Scores of people were evacuated from the area surrounding Alpak Soap, which makes commercial-grade detergent, on Dixon Avenue and about 150 responders from 11 fire departments, as well as hazmat teams and arson detectives, raced to the scene, authorities said.

Alpak workers were mixing chemicals to create chlorine bleach, a process that requires "stirring or agitating" of the chemicals in a 1,200-pound tank, authorities said.

VideoHazmat situation prompts evacuation in Amityville

"They're required to stir it or agitate it," said Kevin Bonner, spokesman for Babylon Town, whose fire marshal is investigating. "It was not done. It began to off-gas."

The gas escaped through the ventilation system at about 5 p.m., he said.

Emergency responders in hazmat suits went inside the plant and determined there was no leak or spillage, authorities said. Amityville Village police and arson detectives interviewed the four workers inside the facility at the time.

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By 6:15 p.m., residents were allowed back in their homes, police said.

But Dixon Avenue remained closed between Albany and Bay View avenues for the cleanup operation that was ongoing Tuesday night, as of 10:30 p.m.

After the business owner and its chemist had evaluated the mishap, they decided to hire an environmental cleanup company to haul away the tank, Bonner said.

"That's the safest way to do it" because of the confined space, he said.

The tank was in the process of being removed late Tuesday night.

Bonner said town officials were pleased that emergency responders handled the accident without any injuries or environmental damage.