Oregon's attorney general today joined nine other states and the District of Columbia in an investigation of fast-food companies who allegedly require employees to sign "no poaching" agreements that keep them from being hired at other franchise locations.

Attorney General Ellen Rosenblum signed onto eight letters asking for more information about the "no poaching" provisions in employment contracts at Five Guys, Dunkin' Donuts, Burger King, Arby's, Little Caesar's, Panera Bread Company, Popeyes and Wendy's. (Disclosure: Rosenblum is married to Richard Meeker, the co-owner of WW's parent company.)

"These "no-poach" agreements appear to be a way for fast food restaurants to prevent low-paid workers from moving up and working for other restaurants in the same chain," Rosenblum said in a statement sent to WW. "Workers should be able to pick up shifts at other franchises, or move to another restaurant that pays more, without fear of losing their job.  These practices are unfair, and we have a responsibility to investigate them."

The Washington Post first reported on the investigation.

Attorneys general in Massachusetts, California, Illinois, Maryland, Minnesota, New Jersey, New York, Pennsylvania, Rhode Island and the District of Columbia are also investigating the fast-food companies' employment rules.