Crews were called around 7:15 a.m. to Weyman Avenue near Bayard Street.
A toxic cloud of chlorine gas sickened about a dozen people.
Police believe it was a mistake by a worker who mixed up chemicals.
As CBS2's Tony Aiello reports, patients needed oxygen to help clear dangerous chlorine gas from their system. First responders treated a lifeguard and swimmers. EMTs also toweled people down to remove chemical residue that could irritate the skin.
One man was swimming when he realized something was terribly wrong.
"Couldn't breath anymore. Obvious mistake in mixing chemicals. Next thing you know, it's just an act of desperation to get out of the pool. Everyone is coughing, desperately trying to get out any which way. Just an awful scene," said Nikolai Pamukoff.
"I was on a stationary bike, multiple people came running out, choking, coughing," said Adam Holmes.
"Respiratory injuries, some skin exposure injuries," said New Rochelle Fire Chief Andrew Sandor.
Sandor said 13 people were taken to local hospitals after exposure to the dangerous fumes.
A source told Aiello that a chlorine was mistakenly mixed in hydrochloric acid, creating a toxic cloud of chlorine gas that quickly spread from a maintenance room near the pool.
"When these two chemicals are mixed, they start to - it's called off-gassing, caused a reaction, and makes the whole atmosphere around unsafe," Sandor said.
Aiello spoke off-camera with a Y manager, very upset at the danger faced by clients and staff. He said the operation to add chemicals to this barrel had been done safely hundreds of times before.
As the mass casualty incident wound down, first responders went through a decontamination process to remove any remaining traces of the dangerous toxic chemicals they were exposed to.
The incident happened early in the day, about 40 minutes before the Y gets crowded with children attending various programs.
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