WICHITA, Kan. (AP) -- Workers at a Kansas slaughterhouse are seeking unpaid wages and overtime from National Beef Packing Co. in a federal lawsuit filed Tuesday on behalf of some 2,000 employees at the firm's Liberal plant.

At issue is the practice of paying meat-processing workers based on so-called gang time, which counts only the time the production line is running. The suit claims employees are not paid for the time it takes them to put on and take off protective gear.

Similar lawsuits over gang-time pay were filed last year against Creekstone Farms Premium Beef in Arkansas City, Kan., and last month against the Farmland Foods slaughterhouse in Monmouth, Ill.

National Beef did not immediately return phone messages left Tuesday seeking comment.

The lawsuit filed Tuesday in U.S. District Court in Kansas seeks class-action status and names employees Valente Sandoval Barbosa and Carolina Gaytan as its class representatives for all hourly meat processing workers.

It claims employees have been systematically underpaid for the time it takes to take off and put on protective gear during unpaid meal breaks, walking to and from production lines, waiting in line for equipment, waiting in line to clean equipment and cleaning equipment. It also contends they were not paid while waiting when the production line was not running.

Mark Kistler, the Overland Park attorney who filed all three lawsuits, said in a phone interview that "gang time" is used throughout the meatpacking industry.

"I am well aware violations of the law in this industry are pervasive," Kistler said. "Unless and until meat processing employers stop breaking the law, I will be more than happy to sue them."

Janet Riley, the spokeswoman for the industry trade group American Meat Institute, said in an email that apparently neither National Beef nor her organization had seen the lawsuit, which makes it tough to comment. She said there have been a number of cases like this.

"Sometimes the courts have found in favor of plaintiffs and sometimes they have found the opposite, so I don't think it's quite the way the attorney wants to characterize," she said.

The lawsuit seeks unspecified damages for unpaid wages along with attorney fees and court costs.