Pro-union workers at Tesla’s Fremont factory are worried about safety at the plant as Tesla CEO Elon Musk and the company enter Model 3 “production hell.”

Two pro-union workers at the Fremont facility told Business Insider that there could be issues with the production line and worker safety.

Tesla allegedly skipped a trial on new assembly line equipment, and issues with that equipment could lead to worker injury, according to the two workers.

In addition to assembly line tests, the workers expressed concern for the “production hell” that will descend on the factory this fall.

Because of the heightened expectations surrounding production, the two workers fear that excessive overtime may be required of staff and could lead to overworked, tired workers and thus injuries.

As production of the Model 3 ramps up, unionization efforts have begun by some workers at the plant. Tesla has worked to adjust its production line in response, but the workers contend that more still needs to be done.

The workers’ claims oppose those made by Musk concerning how refined and efficient the Model 3 production process is expected to be.  

“We’ve gone to great pains with the Model 3 to design it for manufacturing and to not have all sorts of bells and whistles and special features,” Musk said in May during a first-quarter earnings call. “We’ve designed it to be easy to make.”

The inside information comes as Tesla prepares to deliver its first high-volume, affordable EV. However, in addition to these workers’ concerns, BI also highlighted that Tesla has taken a bit of a risk by not undergoing a prototype production phase for the Fremont plant.

While the plant was shut down a few months ago to install equipment for Model 3 production, the company skipped the “soft tooling” phase that would allow the company to work out production issues with disposable equipment and fine-tune its process.

Some workers worry about how the plant will handle the massive production increase that is expected.

“I have my doubts with that because, just like anything new, there are always going to be adjustments that need to be made and you can’t guarantee a flawless, injury-free line right off the launch,” Michael Catura, a Tesla battery production associate, told the outlet. “You’re going to have to deal with all the bugs, all the kinks.”

This news comes a little over a week after a group of Tesla employees wrote a letter to the independent members of the company’s board of directors pushing for access to Tesla’s safety plan, clarity on compensation and neutrality, and non-retaliation agreements in an effort toward unionization. The letter and unionization efforts were led by the “Tesla Workers’ Organizing Committee” and posted on union-backed website fairfutureattesla.org.

With a major bond offering on the table and Tesla’s final test as an automaker rapidly approaching, Musk is surely hoping that any controversy dies down so production can go off without a hitch.