(Bloomberg) -- Amazon.com Inc. has fired a leader of the union campaign in Alabama, according to the Retail, Wholesale and Department Store Union. 

Jennifer Bates was terminated after taking medical leave for injuries sustained working at an Amazon warehouse in Bessemer, Alabama, the union said Friday in a press release. She sought a doctor’s review at the company’s request and was terminated days after returning to work, the union said.

“For them to treat me like this is unfathomable,” Bates said in a statement. “But let me be clear, ‘Amazon, your termination of my employment will not stifle workers organizing, for when you fire leaders, it only brings more people ignited into the movement.’”

The union said Amazon’s app for hourly workers wouldn’t let her submit documentation from her doctors. Stuart Appelbaum, the union’s president, said Bates was terminated “due to a glitch in the company’s own software” and urged the National Labor Relations Board to review her case. “We will continue to hold Amazon accountable and ensure workers’ voices are heard,” he said. 

“Our records indicate that Ms. Bates failed to show up to work for a period of time and didn’t respond or provide documentation to excuse her absences,” Amazon spokesperson Mary Kate Paradis said in an emailed statement. “We work hard to accommodate our team’s needs for personal leaves of absence, but like any employer, we ask our employees to meet certain minimum expectations for leave approval. Ms. Bates has the opportunity to appeal the decision.”

Read more: Amazon Upstart Union Pauses NYC Campaign as Momentum Fades

Amazon’s Alabama warehouse is the site of a closely watched union vote that remains too close to call almost three years after Bates and her colleagues began organizing. The labor board is reviewing the union’s claims that Amazon acted illegally during a re-vote at the facility, which was held last year. Amazon led by more than 100 votes at the end of counting though more than 400 contested ballots have yet to be reviewed. 

Darryl Richardson, another outspoken union organizer in Bessemer, was fired in January. Richardson said at the time that he wasn’t given a reason. Amazon said the firing wasn’t related to his union efforts. The union says Richardson has an unfair labor practices charge pending with the NLRB. 

The labor board’s general counsel has repeatedly accused Amazon of illegally firing activists, but the company has denied wrongdoing. 

(Updates with comment from Amazon in the fifth paragraph.)

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