At least 100 workers at the construction site for Tesla Motors Inc.’s battery factory near Reno, Nevada, walked off the job Monday to protest use of workers from other states, a union official said.

Local labor leaders are upset that Tesla contractor Brycon Corp. is bringing in workers from Arizona and New Mexico, said Todd Koch, president of the Building and Construction Trades Council of Northern Nevada.

“It’s a slap in the face to Nevada workers to walk through the parking lot at the job site and see all these license plates from Arizona and New Mexico,” Koch said in an interview. Those who walked out were among the hundreds on the site, he said.

Construction work at the $5 billion, 10-million-square-foot factory has been proceeding ahead of schedule. Tesla said in an e-mailed statement that the nonunion contractor involved in the dispute Monday, which it didn’t identify by name, is using more than 50 percent Nevada workers and that more than 75 percent of the factory workforce is residents of that state. Tesla didn’t say how the walkout is affecting work at the site.

“Today’s activity stems from the local Carpenters Union protesting against one of the third-party construction contractors that Tesla is using,” the automaker said. “Their issue is not with how Tesla treats its workers.”

Brycon, based in Rio Rancho, New Mexico, didn’t immediately return a phone call requesting comment about the walkout. 

In a letter to shareholders earlier this month, Tesla said that it has begun manufacturing energy-storage devices, including the Powerwall for homes, at the plant. In September 2014, Tesla Chief Executive Officer Elon Musk and Nevada Governor Brian Sandoval announced a deal that included as much as $1.25 billion in tax breaks over 20 years and a requirement that half the so-called gigafactory’s expected 6,500 permanent positions go to Nevada residents.