Elon Musk called an attempted cyberattack against Tesla “serious,” a comment that confirms the company was the target of a foiled ransomware attempt at its massive factory near Reno, Nevada.

The Justice Department released a complaint Thursday that described a thwarted malware attack against an unnamed company in Sparks, Nevada. Tesla has a factory in Sparks that makes battery cells, packs and electric motors; while Tesla was not named in the complaint, several blogs, including Electrek and Teslarati, reported that the company was the target.

The Justice Department alleged that Russian national Egor Igorevich Kriuchkov, 27, attempted to recruit and bribe a Tesla employee to introduce malware in the company’s network.

The malware was designed to install ransomware, a kind of malware that encrypts a victim’s files in exchange for a ransom. Prosecutors said the ransomware used an increasingly popular new tactic that not only encrypts a victim’s files but also exfiltrates the data to the hacker’s servers. The hackers typically threaten to publish the victim’s files if the ransom isn’t paid.

An unnamed employee at the Tesla factory, known as the Gigafactory, met with Kriuchkov, who allegedly offered to pay him $1 million to introduce malware into the computer network. The employee informed Tesla, which then notified the Federal Bureau of Investigations. The FBI used the employee in a sting operation.

Kriuchkov was arrested August 22.