One employee was seriously hurt and two other sustained minor injuries when the low-pressure press spilled hot metal shortly before noon, said Greg Siggins, a spokesman for the California Occupational Safety and Health Adminstration.
"Hot metal somehow burned the workers," said Siggins, who added that there was no fire inside the plant.
The most seriously injured Telsa worker received chest and upper-body burns, Cal-OSHA spokesman Peter Melton said. The three workers were taken to Santa Clara Valley Medical Center in San Jose with second-degree burns, Siggins said.
One of workers was released Wednesday afternoon, hospital spokeswoman Joy Alexiou said. She could not disclose the workers' identities or conditions due to privacy laws.
Telsa CEO Elon Musk said in an email Wednesday that he planned "to visit them in the hospital later today and will personally ensure that they receive the best possible care."
The incident was being treated as an industrial accident, Siggins said.
"We will be talking to any witnesses, reviewing training documents and manuals to see if they are in accordance with specifications as part of finding out what happened," Siggins said.
Tesla Motors, which is headquartered in Palo Alto, makes its all-electric Model S sedan at the Fremont factory. Tesla took ownership of the former plant jointly-owned General Motors and Toyota four years ago and has transformed a portion of the cavernous auto plant into a state-of-the-art facility.
Wednesday's accident follows recent Telsa car fires in Washington state, Tennessee and Mexico that made headlines. Two Model S sedans caught fire after hitting a metal object in the road and a third caught fire after a high-speed chase.
None of the drivers were injured.
Musk said Tuesday that there are no plans for a recall and insisted the Model S is one of the safest cars on the road.