A Massachusetts Buffalo Wild Wings is under investigation after a chemical mixture inside the kitchen killed one employee and left at least 10 staff members and customers hospitalized Thursday, authorities said.

According to Boston’s WHDH-TV, the fire department responded to the restaurant chain, in the town of Burlington, Mass., just after 5:30 p.m. A team of firefighters wearing hazmat suits found a male worker suffering from nausea.

Interim Burlington fire chief Michael Patterson said at a news conference Thursday that the man had been exposed to the chemical, which was being used to clean the floor, after another individual mixed it and became ill.

The man, who has not yet been named, was rushed to a hospital, where he later died. Authorities said that at the time he inhaled the fumes, he was trying to save others from the chemical.

The food chain made headlines earlier this week. On Wednesday, staff at a Buffalo Wild Wings in a strip mall in Naperville, Ill., ordered a mostly African American group of customers to switch tables because another patron did not want to sit next to black people.

The troubling example of public discrimination was captured online and went viral.

A statement released Thursday by a Buffalo Wild Wings spokesperson said, “We are shocked and saddened to learn of this horrific accident at our franchise-owned sports bar and are working closely with our franchisee and the authorities while they conduct an investigation.”

Local authorities continue to investigate the incident. Patterson urged people who were at the restaurant Thursday to seek medical attention.

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