Nevada OSHA confirmed that the U.S. Occupational Safety and Health Administration had received a complaint about the state agency and had opened a federal review into whether Nevada OSHA was at least as effective as the federal agency—a requirement for all state OSHA plans under U.S. law.

The federal inquiry comes about one month after Fortune published an investigation revealing that Nevada OSHA had issued three “willful” and serious citations to Boring Company, the tunneling venture founded by Elon Musk that is digging an underground Tesla tunnel system below Las Vegas and the broader county. The citations were handed to Boring after two firefighters were burned by chemicals in one of its tunnels during a training drill. Shortly after the citations were issued earlier this year, Boring Company’s president called a member of Nevada Gov. Joe Lombardo’s office and set up a meeting with senior state officials, and the state agency rescinded those citations within 24 hours. The removal of the citations was not documented in the case file, and a line item in Nevada OSHA’s case diary that described the meeting was later deleted from a public record, Fortune found. 

Nevada OSHA and the state agencies that sit above it have maintained that Nevada OSHA withdrew the citations after the phone call because it determined that the citations had not met legal requirements, and were therefore not valid. Nevada OSHA has also said that the governor’s office regularly receives complaints from businesses in the state and that this instance only stands out “due to the high-profile nature of the business because of its affiliation with Elon Musk.”

Lawyers and regulators in the state, however, said the handling of the citations violated OSHA’s standard procedure, and the episode sparked outrage among some politicians, including Nevada Congresswoman Dina Titus, who sent a letter to Governor Lombardo urging him to hold Elon Musk’s tunneling company accountable, make the company’s meetings with Nevada OSHA public, and answer a series of questions about how the investigation was handled. A spokeswoman for Nevada Sen. Catherine Cortez Masto also told Fortune that Cortez Masto’s office “supports inquiries to ensure that the Boring Company was made to follow and comply with all OSHA rules.”

It’s unclear at this time who filed the complaint that sparked the federal investigation, formally called a Complaint About State Plan Administration or a CASPA, nor precisely when it was filed. The Labor Department’s records office confirmed that a CASPA had been filed against Nevada OSHA, though it declined to provide the complaint because it is “part of an enforcement proceeding” and “could interfere with OSHA’s ability to effectively enforce the law.” Separately, a Labor Department spokeswoman said that federal OSHA doesn’t comment on state plan investigations or determinations.

These types of inquiries typically take fewer than 60 days to complete, according to OSHA’s policy manual, which details the process. During an investigation, the regional office will review Nevada OSHA’s case file, interview state plan officials and employees as well as other individuals involved. The regional office would also review the effectiveness of the state plan’s policies and procedures, according to the manual. Nevada OSHA itself will have 30 days to respond to the CASPA, and the state agency’s own determination will be considered in the investigation, the manual shows.

This is not the first time that Nevada OSHA has been under scrutiny from federal OSHA. In 2009, federal OSHA initiated a “special study” into the plan after the Las Vegas Sun reported on the agency’s handling of fatalities during the construction of the CityCenter project on the Las Vegas Strip.

Jordan Barab, who initiated that study into Nevada OSHA during his time leading the federal agency under the Obama administration, tells Fortune that, because of the high-profile nature of this new inquiry, the top leaders of the federal agency have likely been looped in. “This would definitely have come to the attention of the assistant secretary, and probably beyond, given that it involves Elon Musk,” Barab says.

Barab suggested that, should federal OSHA find deficiencies with Nevada’s state plan, the regulator could direct Nevada to make corrections to this specific case or amend the agency’s procedures. 

Since the 2009 special study, Barab said that Nevada OSHA had “cleaned up their act” and “appointed some very responsible, competent people to run the program.”

In OSHA’s latest annual report on the Nevada state plan, which was published in 2024 and is publicly available on the regulator’s website, federal OSHA said that Nevada’s state plan had made notable improvements to its workplace culture and staff retention rates—with 95% of positions filled—but criticized the agency’s documentation process, saying that documents had been missing from its case files.