On April 11, Robert Sumwalt, the chairman of the National Transportation Safety Board, called Tesla CEO Elon Musk to tell him that the federal agency was taking the unusual step of removing the company from its investigation into a fatal March 2018 Tesla X crash in California.

Now, as Bloomberg reports, Sumwalt says that Musk abruptly ended the call, according to remarks that the safety official gave before the Society of Air Safety Investigators' Mid-Atlantic Regional Chapter dinner on Thursday.

"Best I remember, he hung up on us," Sumwalt said.

In a short email sent to Ars, Christopher T. O'Neil, the NTSB's chief of media relations, confirmed Bloomberg's description of the call.

"The account of the Chairman's remarks is accurate," O'Neil wrote.

Meanwhile, a Tesla spokesperson declined to comment.

On April 12, the NTSB formally removed Tesla as a party to the investigation into the crash.

"The NTSB took this action because Tesla violated the party agreement by releasing investigative information before it was vetted and confirmed by the NTSB," the agency wrote. "Such releases of incomplete information often lead to speculation and incorrect assumptions about the probable cause of a crash, which does a disservice to the investigative process and the traveling public."

For its part, Tesla said, in fact, that it withdrew before being booted out of the investigation.

A spokesperson even said that the NTSB was "more concerned with press headlines than actually promoting safety."

The NTSB expressed its frustration after Tesla published a March 30 blog post that essentially blamed the man behind the wheel, Walter Huang.

However, Huang's family told local television station ABC 7 that, before the fatal March 23 crash, Huang had taken his car into the Tesla dealership complaining about problems with Autopilot. But Tesla says it has no record of this.

Elon Musk did not immediately respond to Ars' request for comment on Friday afternoon.