Aspiring vehicle maker Nikola (NASDAQ:NKLA) reported quarterly results on Monday for only the second time as a public company. But it wasn't the operation results that caught some investors' attention. 

The company, which plans to make battery-electric and hydrogen-electric trucks, disclosed that it had previously received several subpoenas related to accusations made by short-seller firm Hindenburg Research earlier this year. On Sept. 14, Nikola disputed many accusations made by Hindenburg four days earlier, calling the report "false and defamatory."

It said in its filing that it began receiving subpoenas from the Securities and Exchange Commission and the Justice Department on that date. 

Nikola Tre 1 semi truck

Image source: Nikola.

Nikola reported that the company, as well as officers and employees, received multiple subpoenas from the SEC "as part of a fact-finding inquiry" related to Hindenburg's report. Company directors also received them as late as Sept. 30.

Additionally, founder and former executive chairman Trevor Milton received grand jury subpoenas from the U.S. Attorney's Office for the Southern District of New York. The company also received a grand jury subpoena from the Manhattan District Attorney's office on Sept. 21. Milton announced his resignation from the company on that same day. 

The company says it "has cooperated, and will continue to cooperate, with these and any other regulatory or governmental requests." 

The Hindenburg report came two days after Nikola and General Motors (NYSE:GM) announced a new partnership in which GM would take a $2 billion equity stake in the company, representing 11% ownership. The controversy disrupted those plans, and negotiations are reportedly ongoing, since the deal has yet to close. 

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