A group of fast-food workers in Chicago says McDonald's is doing too little to protect them despite what they describe in a lawsuit as a "nationwide pattern" of violence at the company's restaurants.

The complaint, filed Thursday by 17 employees, alleges that McDonald's and its franchises disregard worker safety by keeping stores open late into the night and by remodeling its stores in a way that leaves workers more vulnerable to assault.

All of the workers filing the suit were either victims of violence or had witnessed violence against their coworkers, Danny Rosenthal, the lead attorney in the case, told reporters in a conference call on Thursday. The incidents include a customer jumping over a counter and pulling a gun on workers, and another guest beating an employee with a wet-floor sign.

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An average of 20 calls are made to 911 each day from McDonald's stores in Chicago, said Rosenthal, a partner at law firm James & Hoffman. The call was organized by the union-backed "Fight for $15" movement, which advocates on behalf of fast-food and other low-wage workers.

The workers filing the suit also claim that McDonald's doesn't provide basic safety training for most managers and employees and plasters restaurant windows with ads, reducing visibility.

"The incidents described in this complaint are not random or unforeseeable," according to the suit. "They are the result of choices made by McDonald's that undermine safety."

McDonald's "takes seriously its responsibility to provide and foster a safe working environment for our employees, and along with our franchisees, continue to make investments in training programs that uphold safe environments for customers and crew members," the company said in a statement. "In addition to training, McDonald's maintains stringent policies against violence in our restaurants."

In the past, McDonald's has argued it should not be held accountable for franchisees and their workers. A federal appeals court ruled in October that the fast-food giant did not exert enough control over franchisees' workers to be viewed as a joint employer liable for their treatment.

Preventing physical contact

McDonald's workers face a greater risk of violence in part because of the design of the company's restaurants, according to the suit. Lowered and split counters make it easier for people to jump over or walk into work areas, they contend.

The suit seeks a court injunction to block McDonald's from completing a $6 billion upgrade of its stores nationwide that began last year. About 1,500 McDonald's restaurants have been upgraded this year, and the company remains on track to finish about 2,000 more by year-end, according to McDonald's, which did not respond to requests for comment.

J.R. Roberts, president of J.R. Roberts Security Strategies, said in the news conference that McDonald's ignored known ways of protecting workers, pointing to a recent incident in Virginia in which an employee was reportedly beaten by two customers who pulled the cashier through a drive-thru window. "There are security windows that could be used that would prevent physical contact," Roberts said.

Employees at one McDonald's outlet in Chicago in May filed a report with the Occupational Health and Safety Administration saying their workplace had been the scene of 31 violent incidents over six months during the past year.

— The Associated Press contributed to this report.