A federal grand jury has charged Trevor Milton, the founder and former executive chairman of electric-vehicle startup Nikola, with three counts of fraud related to claims he made about the company's planned products.

The Securities and Exchange Commission has also filed civil securities fraud charges against the 39-year-old billionaire.

The indictment, details of which can be read at the Department of Justice website, alleges that Milton made “false and misleading” claims about Nikola's products and technology to the investing public.

Alleged false claims made by Milton include one that Nikola had a functioning semi-trailer truck prototype, another that the company had developed a pickup truck, and another that the company was producing its own hydrogen. Also mentioned was the now infamous video posted on Milton's Twitter account of a truck driving along a flat road, which was allegedly filmed by having a non-functioning truck towed to the top of a hill and then rolled down.

Milton pleaded not guilty to the charges and is currently out on bail.

Nikola Tre

Nikola Tre

Nikola over the years has rolled out various vehicles including the Badger pickup truck; One, Two and Tre semi-trailer trucks; and NZT utility task vehicle.

In a statement published to its website on Thursday, Nikola said it is cooperating with the inquiry and remains committed to its previously announced milestones and timelines, including delivering the first examples of the Tre battery-electric truck later this year.

Milton, who at one point owned 20% of Nikola, stepped down from the company last September after the DOJ and SEC started probing Nikola over allegations of fraud brought up by investment company Hindenburg Research.

Hindenburg Research, which called Nikola an “intricate fraud” in a report published Sept. 10, was first to claim that Milton falsely claimed to have proprietary technology, and that the company used mockups in its promotional videos instead of functioning vehicles.

It was about this time that Nikola announced a deal that it would source hydrogen powertrain technology and production capacity from General Motors, though GM scaled back the deal the following November to only supplying powertrains.