New York CNN Business  — 

The union that was the first to win a representation vote at an Amazon facility has filed for an election among about 400 employees at another Amazon distribution center.

The facility is in suburban Albany, New York. The National Labor Relations Board, which oversees union representation votes, has confirmed the filing but has yet to verify the signatures of the employees who signed cards asking for the vote. At least 30% of the employees in a potential bargaining unit need to sign cards for an election to be held.

“We’re proud and happy for these workers to be standing up and fighting for their rights,” said Chris Smalls, president of the Amazon Labor Union, which won the vote at an Amazon facility on Staten Island, New York, in April, but lost the vote at a second nearby facility in May.

Smalls said he is talking to employees who are working to hold elections at other facilities across the country, although he wouldn’t say how many organizing campaigns are underway.

“There will be plenty more to come after that in short order. It’s growing every week,” he said. “All we can do is continue to build and organize. Hopefully the company will change their outlook once they see this is something not going away.”

An Amazon (AMZN) spokesperson said the company had only received the petition from the NLRB Wednesday morning.

“Our employees have the choice of whether or not to join a union. They always have. As a company, we don’t think unions are the best answer for our employees,” said the company’s statement. “Our focus remains on working directly with our team to continue making Amazon a great place to work.”

Amazon continues to challenge the results of the April vote it lost in Staten Island and has yet to negotiate an initial contract with the union.

A separate union has lost two votes to represent workers at a different Amazon facility in Alabama, though that union is challenging the results of the most recent vote.

While a bit more than one third of government workers are members of a union, according to Labor Department statistics, only 6.1% of workers employed by businesses are union members. And those private sector union members are concentrated in a few specific industries, such as manufacturing, airlines, construction and health care. Only 4% of retail workers are union members.

But there has been a growing effort to win union representation in the service sector, which is the largest employment sector in the US economy. About 200 Starbucks stores have voted in favor of representation by a union since the first victory at a store last fall in Buffalo, New York.