The acting head of the National Labor Relations Board (NLRB) said Google “arguably violated” US labor law by illegally firing three workers in 2019 amid their organizing activities, Bloomberg reports. On Wednesday, the NLRB reversed an earlier decision which had dismissed claims from Sophie Waldman, Rebecca Rivers, and Paul Duke that Google had retaliated against them for labor activism.

The NLRB’s general counsel’s office has already accused Google of unlawfully terminating former Google workers Laurence Berland and Kathryn Spiers. Now, acting general counsel Peter Sung Ohr has asked that the complaint be amended to include Waldman, Rivers, and Duke.

Google claims that four employees, Berland, Waldman, Rivers, and Duke, were fired for violating data security policies; the employees say that’s not true. They argue the firings were retaliation for trying to organize in the workplace, and that Google terminated them to send a message to other employees. Rivers and Berland say that the documents they accessed weren’t sensitive, and that they were monitoring public calendar events. Spiers was fired for allegedly bypassing proper code submission procedures — she says she did a routine update to an internal system to remind employees of their labor rights. The trial is set to begin in June.

In a statement emailed to The Verge, a Google spokesperson said: “Our thorough investigation found the individuals were involved in systematic searches for other employees’ materials and work, including distributing confidential business and client information. As the hearing on these matters moves forward, we’re very confident in our decision and legal position.”