A purported Department of Justice criminal investigation looking into any personal perks Elon Musk may have received from Tesla during his time as chief executive goes back further than previously known, according to The Wall Street Journal, which first reported the probe.

Citing people familiar, the Journal reported Tuesday federal prosecutors have now dug back as far as 2017 as they seek information on whether Tesla resources were used for Musk's personal benefit, including an alleged secret project dubbed "Project 42" to build Musk a glass house near the electric vehicle giant's headquarters in Austin, Texas, as well as transactions between Tesla and other companies linked to Musk.

The Journal further reported that the Securities and Exchange Commission (SEC) and Tesla board members have also launched probes into whether the company's resources were used for "Project 42."

Earlier this month, Musk denied on X – the social media platform formerly known as Twitter that he acquired last year – that he had any house plans in the works at all. 

ELON MUSK DENIES REPORT THAT TESLA IN TALKS WITH SAUDIS ABOUT OPENING FACTORY

"Just want to reiterate that there is no glass house (metaphors don’t count lol) built, under construction or planned," the billionaire wrote. "I’m not building any house of any kind anywhere. Period."

The Journal noted that Musk did not "address past work or plans," and "neither he nor his representatives have responded to requests for comment."

GET FOX BUSINESS ON THE GO BY CLICKING HERE

Neither Tesla nor the Department of Justice immediately responded to FOX Business' request for comment on The Wall Street Journal's reporting.