Trader Joe's has been accused of violating workers' rights after supervisors allegedly removed union literature from an employee break room last year at the grocery chain's downtown Minneapolis store.

The incident occurred months after workers had voted to unionize. According to a new National Labor Relations Board complaint, the union filed the unfair labor practice charge this past November after the removal of the pro-union papers. A notice subsequently posted on a bulletin board in the break room read: "The break room space is reserved for company business, [w]hich is not to be used for any other purpose."

Trader Joe's conduct could fall under the part of the National Labor Relations Act that says employers shouldn't unfairly interfere, restrain and coerce employees in the exercise of their rights to organize. There is a hearing scheduled for this October.

Trader Joe's did not immediately respond to a request for comment.

"While we're disappointed that Trader Joe's wouldn't agree to settle in this case, we are thrilled to be making progress on this and the countless other unfair labor practice charges we've filed against our employer," Trader Joe's United said in a statement Thursday. "This is just the beginning of holding Trader Joe's accountable for the many instances in which they've violated our rights as workers, and we're looking forward to the hearing in October."

Last August, Trader Joe's on Washington Avenue in the Mill District area of Minneapolis, became the second in the grocery's national chain to unionize after a store in Hadley, Mass. Safety concerns were one of the most-cited reasons for the union effort.