The National Labor Relations Board will hold a hearing on May 7 to review objections to a recent union election at one of Amazon’s Alabama warehouses, according to the union that led the campaign.

In an April 16 complaint, the Retail, Wholesale and Department Store Union accused Amazon of interfering in the closely watched union campaign held earlier this month at the company’s Bessemer, Alabama, warehouse. Bessemer employees overwhelmingly rejected unionization, with fewer than 30% of the votes tallied in favor of joining the RWDSU.

The RWDSU requested that the NLRB set aside the election results because of Amazon’s alleged interference. The union accused Amazon of retaliating against pro-union employees, threatening widespread layoffs and closing the facility if employees voted in the union, among other complaints.

Amazon has rejected the NLRB’s claims that it interfered in the election. “Rather than accepting these employees’ choice, the union seems determined to continue misrepresenting the facts in order to drive its own agenda,” Amazon spokeswoman Heather Knox previously told CNBC.

The hearing will be overseen by the NLRB’s regional director, who has the power to throw out the results. Either party can appeal the regional director’s ruling to the NLRB board in Washington, which can also order a new election.

Amazon and the NLRB didn’t immediately respond to a request for comment.