New York (CNN) -- A restaurant manager died and one of his employees remained hospitalized after inhaling carbon monoxide at a Long Island mall, authorities said Sunday.
Another 26 people were treated and released after the incident, according to hospitals.
Police and emergency crews rushed to Walt Whitman Shops in Huntington Station, New York, on Saturday night after reports that a woman had collapsed in the basement of Legal Sea Foods. Once they arrived, they felt dizzy as well and determined that the cause was carbon monoxide poisoning, said police in Suffolk County, New York.
"Police evacuated the restaurant and found the manager, Steven Nelson, 55, of Copiague, unconscious in the basement," a statement said. "He was transported to Huntington Hospital where he was pronounced dead."
A sign on the restaurant's door Sunday said the building has been condemned as being unsafe and unfit for human habitation.
Investigators found a leak in the flue pipe of the water heater, said A.J. Carter, a spokesman for the town of Huntington.
Authorities sent the restaurant a summons for faulty equipment, which carries a fine of up to $2,000, Carter said.
Colorless, odorless carbon monoxide is produced by the incomplete combustion of fossil fuels like oil and natural gas.
The restaurant didn't have a carbon monoxide detector. State fire codes require them only in establishments where people sleep, Carter said.
Legal Sea Foods is subject to annual inspection, and there were no issues when a town official inspected the restaurant in March. The restaurant was scheduled for another inspection at the end of next month.
The restaurant and surrounding businesses were evacuated as a precaution Saturday, but authorities said the carbon monoxide appeared limited to the basement of the restaurant.
National Grid, the restaurant's natural gas provider, shut off a gas line shared by Panera Bread and Legal Sea Foods as a precaution, Carter said.
Before either restaurant can reopen, he said, they'll have to get plumbers to check for leaks and receive certification from the town's plumbing inspector.
Boston-based Legal Sea Foods offered its condolences to Nelson's family and said it planned to check safety at all of its restaurants as a result of the incident.
"The terrible tragedy highlights the inadequacy of the codes for carbon monoxide detectors in commercial spaces. In the wake of Saturday night's tragic events, I have instructed our operations team to conduct an exhaustive safety check at all our restaurants. This includes not only ensuring that we meet local codes as we did in Huntington, but putting a plan in place to exceed them in order to safeguard everyone," Legal Sea Foods CEO Roger Berkowitz said in a written statement. "Stronger safety measures must be put in place, and I pledge to be at the forefront of this effort."
Grief counselors will be meeting with the restaurant's associates, and their family and friends, Berkowitz said.
"Steve's tragic death is a shock to all of us at Legal Sea Foods," he said. "He was one of the finest people we've ever had the pleasure of working with."
CNN's Alexandra Field reported from New York. CNN's Faith Karimi and Joe Sutton reported from Atlanta. CNN's Chris Welch, Catherine E. Shoichet, Chris Kokenes, Susan Candiotti and Lawrence Crook contributed to this report.