The investigation comes just days after the Center for Investigative Reporting’s Reveal published a lengthy report about worker safety at Tesla’s Fremont factory, where the Model S sedan, Model X SUV, and new mass-market Model 3 is produced. The report uncovered evidence that Tesla had underreported worker injuries to regulators.

However, it’s not clear if the Reveal report or a complaint from a Tesla employee prompted OSHA to launch its investigation. An OSHA spokeswoman said in a statement emailed to Fortune that the agency has an open inspection at Tesla.

“Cal/OSHA takes seriously reports of workplace hazards and allegations of employers’ underreporting recordable work-related injuries and illnesses on the Log 300, the spokeswoman said, referring to the mandated reports that Tesla must submit.

“While we do not disclose details of open inspections, Cal/OSHA’s inspections typically include a review of the employer’s Log 300, as well as a review to ensure that serious injuries are reported directly to Cal/OSHA within eight hours as required by law,” the statement continued. “Cal/OSHA’s regulations define a serious injury or illness as one that requires employee hospitalization for more than 24 hours for other than medical observation, or in which a part of the body is lost or permanent disfigurement occurs.”

Tesla tried to downplay the investigation, saying in a statement that” Cal-OSHA is required to investigate any claims that are made, regardless of whether they have merit or are baseless (as we believe these are), and we always provide our full cooperation.”

The automaker compared its injury rates to operations at the factory when it was operated by Toyota and GM. Tesla’s Fremont factory is the former Nummi plant jointly owned by Toyota and General Motors that produced nearly 430,000 vehicles at its peak.

“The injury rate at our Fremont factory is half what it was in the final years of the UAW plant operated by GM/Toyota immediately before us, and we care deeply about the safety and well-being of our people and strive to do better every day.

Tesla also noted that last year Cal-OSHA investigated Tesla’s injury reporting and record-keeping was closed without any violations found and without any further action taken.

“Unlike other automakers who in the past have been cited by OSHA for record-keeping violations, we have never in the entire history of our company received a violation for inaccurate or incomplete injury record-keeping,” Tesla said in the emailed statement.

The OSHA investigation, first reported by Bloomberg, comes at a critical time for Tesla, which has been plagued by a string of problems in recent months, notably a failure to reach its production targets for the Model 3. Tesla has also been engaged in a public fight this month with the National Transportation Safety Board over its investigation of a fatal Model X crash near San Francisco.

Tesla’s Model 3 production problems were first revealed in early October when the automaker reported it had produced just 260 of its new Model 3 electric cars in the third quarter and delivered only 220. Production improved to 2,425 Model 3s in the fourth quarter and 1,542 deliveries, but it was still below expectations.

Tesla reported in April that it had fallen short of its target to produce 2,500 Model 3s per week by the end of the first quarter. The company produced 2,020 Model 3 vehicles in a week at the end of the quarter, prompting Musk to admit that his reliance on automation had caused production bottlenecks.

Tesla plans to operate its factory all day, every day in an effort to increase weekly production of its Model 3 cars to 6,000 by the end of June, according to an internal email that Musk sent to employees on Tuesday. Musk said the company would add another shift to be able to run the factory 24 hours a day, seven days a week.

But that push could be hamstrung by an investigation that will examine workplace hazards at the plant. Tesla is required by California law to submit Log 300 records of injuries and illnesses. The Reveal report said some of those injuries were not reported, making Tesla’s safety record appear to be better than it was.

Tesla has come under fire for its safety record before. Last May, Worksafe, a worker safety advocacy group, found injury rates at the plant were well above the industry average in 2014 and 2015. Worksafe analyzed reports filed with the U.S. Labor Department’s Occupational Safety and Health Administration and found similarly high injury rates in 2016 at the plant.