Federal officials are counting the votes in the closely watched union election by Amazon.com Inc. warehouse workers in Bessemer, Ala., and results are expected on Friday.

Some Bessemer workers are trying to become the first Amazon employees to be unionized and would be represented by the Retail, Wholesale and Department Store Union. Officials have counted about half the ballots cast.

Of votes counted, about 70% of the Amazon employees sided against unionization Thursday, according to a Wall Street Journal tally. Officials from the National Labor Relations Board counted votes for hours in a broadcast. A total of 3,215 ballots were submitted, and officials will resume counting Friday, when a final outcome could become clear.

The NLRB has processed ballots for days since the voting concluded on March 29 to ensure they were valid, and it allowed both parties an opportunity to contest the eligibility of each one. As the tally swung widely in Amazon’s favor Thursday, The union criticized the company’s tactics during the election, including how it held mandatory meetings to discourage workers from voting in favor of the union and a mailbox that appeared near the Bessemer facility.

The U.S. Postal Service installed a mailbox outside the Bessemer facility close to when the mail vote began in February after requests from Amazon, according to email records viewed by The Wall Street Journal. The union said took issue with the mailbox because it said it could intimidate voting workers to think Amazon was conducting the election.