One person was dead and 10 other people were sickened in a chemical accident at a Buffalo Wild Wings restaurant on Thursday night, Nov. 7, in Burlington, Massachusetts, authorities said.

Burlington firefighters responded around 5:30 p.m. to 15 South Avenue and found an employee suffering from nausea after breathing in the unidentified chemical. He was rushed to Lahey Hospital in serious condition and was later pronounced dead, NBC10 Boston reported.

Interim Burlington Fire Chief Michael Patterson said Super 8, a common sanitation product, was being used to clean the floor by an employee when people inside the restaurant became sick. He described the situation as “a serious hazardous material incident.”

“What we believe happened is a worker at Buffalo Wild Wings used a cleaning agent on the floor. The cleaning agent is Super 8. The chemical definition or chemical identification is sodium hypochlorite,” Patterson said. “What sodium hypochlorite is a high concentration of chlorine.”

Nine other patients drove themselves to Lahey Hospital, according to Patterson, and the 10th person self-checked in a Lowell hospital. Two of the patients are customers; the rest of them are employees. The patients’ symptoms include runny and watery eyes and shortness of breath. None of them were in serious condition.

The Buffalo Wild Wings was evacuated, and a Tier 1 hazmat team has been called. The restaurant was closed for the night.

“Anyone who was in the restaurant at the time and believes they may be impacted by the incident should seek medical treatment immediately,” the fire department said in a statement.

Patterson said that they were not sure whether the product had been mixed with anything else.

The Occupational Safety and Health Administration has been notified of the case, fire officials said.

The investigation is ongoing.