The Wall Street Journal reported on Thursday that US prosecutors have opened an investigation into the alleged use of Tesla funds to build a 'secret house' for the company's executive, Elon Musk.

The US attorney’s office for the southern district of New York is seeking information from Tesla regarding personal benefits paid to Musk, how much money was spent on the project, and its purpose.

Citing sources close to the matter, WSJ said that the Securities and Exchange Commission had also opened a civil investigation into the project -- alternatively known as 'Project 42.'

In a report published in July, WSJ said that plans for 'Project 42' looked similar to Apple's store at Fifth Avenue in Manhattan, New York.

The proposed building would be made almost entirely of glass and have the shape of a twisted hexagon. It would also be located right behind Tesla's Austin factory. 

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While the status of the project and the order of glass is currently unknown, the investigations are in their early stages and may not result in charges, WSJ noted. 

Also in March, WSJ said that Elon Musk was planning to build a kind of self-contained community outside of Austin where his employees could reside and work.

The town-like community would be located near his Boring tunneling company and his SpaceX rocket company.

WSJ also reported on Wednesday that federal prosecutors are investigating Tesla's claims about the performance of its vehicles after a report that the company overstated the potential driving range of its cars.

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Last month, Reuters reported that Tesla vehicles often failed to meet the range estimates advertised by the company or displayed on the cars' own dashboard.

According to sources, Tesla allegedly wrote algorithms ten years ago to create optimistic in-car driving range estimates.

The company also reportedly set up a team to dismiss service appointments for customers who had range-related problems. The carmaker created a team to respond to the many customers who were upset that their cars' range was not as long as they had been led to believe, Reuters added, citing sources.

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