Seven people were transported to the hospital after a chlorine spill in Volusia County.
It happened near the intersection of 3rd Street and Center Avenue Monday night.
Holly Hill Fire Chief James Bland said a tanker was delivering chlorine to a pool supply facility when the driver accidentally pumped the chemical into a sulfuric acid tank, making "mustard gas."
The tanker's driver was taken to Halifax Health Medical Center of Daytona Beach.
Six others, who had difficulty breathing, were also hospitalized.
The leak was responsible for one crash.
"One car accident as a result of this,” Bland said. “(He tried driving through the cloud?) Yeah, he was having some sort of medical problem as he drove through the, I'm not sure if it was a cloud. I don't know what he was experiencing, but he stopped his car in the middle of the street and he was rear-ended."
The conditions of all patients are unknown.
The fire chief said the rain helped diffuse the situation diluting much of the chemical.
Crews closed one block surrounding the business to traffic.
There were no evacuations.