The voting process opened Monday for Amazon workers at a large US distribution center in a union drive in a major test for organized labor and Big Tech.

Ballots were being mailed to workers at the warehouse in Bessemer, Alabama, and voting will continue through March 29, under an order from the National Labor Relations Board (NLRB).

The count is expected to begin March 30.

Formation of a bargaining unit at the Amazon facility in Alabama would be the first successful effort in the US to unionize workers at the e-commerce titan.

Amazon has argued that the latest union effort lacked support from a majority in Bessemer, while noting that it offers above-average wages and benefits.

Traditionally, the NLRB will authorize a vote when at least 30 percent of a labor force signs union cards. But it was unclear exactly how many of the Bessemer employees supported the effort

Amazon, which has fended off union drives in its vast logistics network, claims it offers benefits and starting pay of $15.30 per hour in a state where the legal minimum wage is less than half that amount.

Amazon warehouse
An Amazon warehouse is pictured. AFP / ERIC PIERMONT

The move comes amid a series of protests around the United States on safety and working conditions with the coronavirus pandemic increasing pressure on Amazon's distribution network.

The company has maintained that it has invested billions in worker safety even as it has boosted the number of its employees

The Retail, Wholesale and Department Store Union, which is conducting the drive, noted that the federal agency supervising the election maintained the mail-in ballots, rejecting Amazon's request for in-person voting.

"Amazon's blatant disregard for the health and safety of its own workforce was demonstrated yet again by its insistence for an in-person election in the middle of the pandemic," union president Stuart Appelbaum said in a statement.

Amazon contended in NLRB filings that the bargaining unit of approximately 5,800 employees was "unusually large," arguing in-person voting would be more manageable.

NLRB officials said in their order denying Amazon's request that there were no substantial issues in need of review and reasoned that the safety of all involved with the voting "is best served, at this time, by avoiding the type of in-person gatherings that a manual election entails."

Amazon is the second largest employer in the United States with more than 800,000 employees, most of whom are "essential workers" who can't do their jobs from home.