More than six people were sent to the hospital after a truck driver made a critical mistake with his delivery to a swimming pool chemical distribution firm in Holly Hill, Fla.

Oliver Spann was in critical condition Jan. 13 as a result of mistakenly pumping 1,000 gallons of bleach into two tanks at Poolsure that contained sulfuric acid, according to the Daytona Beach News-Journal. Seven others also were hospitalized. Authorities warned the 279 residences in a half-mile radius about the noxious vapor, described as a low-grade mustard gas.

Allied Universal, the Miami-based company that delivered the bleach to Poolsure, and its trucking subsidiary Transportation Service Unlimited, who employs Spann, are investigating the incident. The Occupational Safety and Health Administration also began probing the accident Tuesday morning.

Poolsure is a Houston-based chemical treatment products company for aquatic and waste-water treatment facilities in Florida, Texas and Louisiana.

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