NEW YORK — Amazon workers at an upstate New York warehouse began voting Wednesday on whether to unionize in the latest labor battle following a surprise union win earlier this year at another Amazon site.

Amazon Labor Union (ALU), which won a unionization vote in April at the 8,000-employee JFK8 warehouse in Staten Island in New York City, is hoping to follow up that upset with another win at a much smaller Amazon facility near the state capital Albany.

Some 400 full-time hourly workers at the ALB1 site in Castelton-On-Hudson, about 150 miles (240 kilometers) north of Manhattan, will vote between Wednesday and Monday on whether to be represented by ALU.

The National Labor Relations Board, which is overseeing the election, plans to begin counting ballots on Tuesday, October 18.

The NLRB moved ahead with the election after the ALU submitted signatures from more than the 30 percent of employees needed.

Amazon has signaled complete opposition to the effort.

“We remain skeptical that there are a sufficient number of legitimate signatures to support the union’s petition for an election, but the NLRB is moving forward,” said Amazon spokesman Paul Flaningan.

“We’ve always said that we want our employees to have their voices heard, and we hope and expect this process allows for that.”

Led by its president Christian Smalls, a former worker at the Staten Island site, the ALU gave a jolt to the US organized labor movement this spring after a solid majority voted for representation.

However, just weeks later, the ALU suffered a setback when the LDJ5 warehouse, also in Staten Island, voted against the group.

Amazon has refused to accept the election outcome in the first Staten Island vote, arguing the results should be tossed out in light of alleged improprieties.

Last month, an NLRB official rejected Amazon’s claims as groundless after a 24-day hearing on the e-commerce giant’s claims.

Flaningan said Amazon “strongly” disagrees with the NLRB official’s decision and plans to appeal.

The ongoing fight over the election has prevented contract talks between the ALU and Amazon at JFK8.