Police arrested a former employee, according to news reports. The victims were a man and woman who both worked for Cheli's Chili Bar, officials said. They were found shortly after 9 a.m. ET on the restaurant's second floor, said police spokeswoman Yvette Walker.
A former employee was arrested, the Detroit Free Press and Detroit News reported. Earlier, Police Chief Ella Bully-Cummings told the Free Press that "a former disgruntled employee" may have been responsible.
The newspapers identified the victims as Megan Soroka, 49, of suburban Dearborn, and Mark Barnard, a 52, of Detroit.
Soroka was a manager and Barnard was a cook, the papers said.
Police also questioned other employees in the restaurant at the time of the killings, believed to be shortly before 9 a.m. The three-story building sits next to Comerica Park, home of the Detroit Tigers.
"We are deeply saddened by the tragedy that occurred at our establishment this morning," Chelios said in a statement. "Our hearts go out to the families of the victims - they were wonderful employees and were part of our family."
Chelios opened the sports bar and restaurant in 2005. The establishment, which has a banner honouring former Red Wings captain Steve Yzerman hanging from an exterior wall, had been expected to have a busy night Tuesday because of a ceremony at Joe Louis Arena honouring Yzerman.
The restaurant planned to remain closed Tuesday night, said spokeswoman Jennifer Cooper.