Many Minneapolis park workers are in the middle of a seven-day strike over stalled contract negotiations.

Monday, the union LIUNA 363 filed an unfair labor practice charge against the Minneapolis Park and Recreation Board, claiming the board tried to intimidate employees who were planning to strike and threatening to lock them out from returning to work.

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“Threatening they would lose their jobs, threatening demotions or taking away seniority… and also telling them they would not be allowed to come back to work until the strike was resolved and the contract has been ratified which is illegal,” said AJ Lange with LIUNA 363.

A spokesperson for the board shared information that was sent out to employees Monday afternoon. It said “The Minneapolis Park and Recreation Board was made aware that striking Local 363 employees plan to return to work on Thursday, July 11. The MPRB will welcome all striking employees back on Thursday. No employee who went on strike will be turned away.”

The two sides have been negotiating for seven months over the terms of a pay raise.

RELATED: Minneapolis park workers go on strike, demanding better wages and benefits

Meanwhile, the Minnesota Orchestra has cancelled three recent concerts at the Lake Harriet Bandshell as a show of solidarity for striking workers.