Chicago’s Congress Plaza Hotel has filed a lawsuit claiming that members of the Unite Here Local 1 sent a heart-shaped package containing cow manure to scientists planning to attend a convention at the hotel to discourage them from participating in the event.

The hotel has been the site of a labor dispute since 2003 when union employees at the hotel went on strike, which is still ongoing.

According to the Chicago Sun-Times, the suit claims that the union "has aggressively harassed, threatened and intimidated numerous secondary employers and their customers and other affiliates in order to bring indirect pressure on the primary employer by involving neutral or secondary employers in the dispute."

The suit didn’t state when the incident occurred. The suit claims that the union’s strike actions have cost the hotel more than $700,000 in revenue and violate the Labor Management Relations Act.