FREMONT – A new study commissioned by Tesla workers found that the electric vehicle maker’s factory in the last two years had about one-third more worker accidents and twice the rate of serious injuries as other auto manufacturers.

The report released Wednesday is the latest salvo in an ongoing dispute between the rapidly growing automaker and workers seeking to unionize the factory. Tesla hopes to jump production from 84,000 electric vehicles last year to a half-million next year, including its lower-cost Model 3 sedan.

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Tesla responds to its critics over workplace safety

Elon Musk, business execs urge Trump to keep U.S. climate promises The study, conducted by the non-profit worker advocacy group Worksafe, found that recorded incidents in 2015 were 31 percent higher than the average auto plant. The rate of serious injury, measured by days away from work, job transfers and restricted duty, was about twice the industry average.

Tesla acknowledged that long work hours and pressure to deliver vehicles have led to taxing factory conditions. But it said it has made broad changes and has improved worker safety.

“We may have had some challenges in the past as we were learning how to become a car company, but what matters is the future and with the changes we’ve made, we now have the lowest injury rate in the industry by far,” a company spokesman said on Wednesday. “Our goal is to have as close to zero injuries as humanly possible and to become the safest factory in the auto industry.”

The company pointed out that safety has improved this year, with recorded accidents one-third less than the industry average. Tesla credits the improvement to adding a third shift, reducing worker hours and placing more emphasis on ergonomics.

The Worksafe report disputes the company’s assertion that the factory floor is getting safer.

“One quarter is not a sufficient length of time to accurately identify a meaningful and lasting trend in injury reduction,” the report said.

Doug Parker, executive director of Worksafe, said the company updated its injury numbers this month, adding significantly more incidents to its 2016 totals.

“We’re just not that confident about Tesla’s numbers,” he said.

He said increased demands on workers making a new vehicle, the Model 3, could mean significant changes to the factory in the months and years ahead.

“There’s going to be a whole new health and safety environment,” Parker said. “We hope that Tesla is making strides.”

Parker said the reported injuries, which did not include any fatalities, came mostly from poor ergonomic planning and stress caused by repetitive work.

Factory employees have coordinated with the United Automobile Workers and are seeking to unionize the plant.

In the midst of the labor unrest, Tesla announced a shake-up Tuesday in its human resources department. Arnnon Geshuri, who led the Human Resources department at Tesla for more than eight years, is leaving. Gaby Toledano,a former executive at Electronic Arts, was named chief people officer, reporting to CEO Elon Musk and leading Human Resources and Facilities departments.

Tesla employs about 10,000 workers at its Fremont factory and 30,000 around the globe.

The company is facing a lawsuit from a factory worker who claimed he was subjected to racists taunts by co-workers, and also injured on the job. The company settled a lawsuit last year involving a seriously injured Slovenian man working at the plant for a subcontractor.

Two Tesla employees spoke Wednesday on the need for better training and safety for production workers. They pointed to the need for more regular hours, better training and ergonomics.

One of the workers, Alan Ochoa, began on the factory floor in 2014, installing speakers and weatherstripping. He eventually learned several other jobs along the production line.

But the long hours, sometimes 12-hour shifts for six days a week, took a toll. Ochoa had two surgeries, he said, and might need a third for repetitive stress injuries.

Other workers are hurting too, he said, but “they’re afraid to say anything.”