Sources among workers working to dig the only tunnel the Boring Company has managed to dig in years say the tunnel is “filled with chemical sludge,” the very fine waste that is a byproduct of the drilling process. Their consistency resembled a milkshake that would burn the skin of anyone who came into contact with it.

Workers reported numerous violations and injuries

Today, in the neon-lit tunnels beneath Las Vegas, Tesla covers just a few kilometers, transporting people to the exhibition center at a speed of no more than 60 kilometers per hour.

Boring Company employees, who declined to give their names for fear of revenge from Musk, said the following during construction in an interview with Bloomberg: In some parts of the tunnel system, mud sometimes reaches a height of 60 centimeters. If it got on the shoes or face, it would burn the skin.

At a construction site beneath the Encore Las Vegas hotel, the chemical slurry was spiked with not only the usual byproducts—sand, silt, and water—but also accelerators used to accelerate the hardening of tunneling mortar. As the mud accumulated, the associated safety risks also increased. According to employees of the Nevada Occupational Safety and Health Administration (OSHA), slime burns were almost a routine occurrence.

The state’s OSHA has launched its own investigation into alleged safety hazards in Boring Company tunnels, according to documents obtained by Bloomberg through a Freedom of Information Act request. some workers were permanently injured from burns.

In addition to regularly burning people, the slime literally covered the tunnel in other dangerous ways. Last summer, for example, an intern was nearly crushed when two-ton concrete containers collapsed because the metal supports were overloaded with material. Luckily no one died.

The agency fined Boring more than $112,000 for eight violations that it described as “serious.” The company is appealing that decision, as Musk’s companies usually do.

Overpromising and underpromising in the workplace is commonplace when it comes to Elon Musk’s companies. But toxic sludge is something new.