Elon Musk said on Monday that Tesla is working to get an updated version of the self-driving software out for vehicles soon and that the latest released version “is not great.”

The Full Self-Driving Beta version 9.2 is "actually not great imo (in my opinion), but Autopilot/AI team is rallying to improve as fast as possible," Musk posted on Twitter.

"We're trying to have a single stack for both highway & city streets, but it requires massive NN (neural network) retraining."

The statement comes after a recent investigation was called by Senate Democrats Richard Blumenthal of Connecticut and Edward Markey of Massachusetts to review Tesla's autopilot software.

"Tesla and (CEO) Mr. (Elon) Musk’s repeated overstatements of their vehicle’s capabilities ... put Tesla drivers – and all of the traveling public – at risk of serious injury or death," Blumenthal and Markey said in a letter to FTC Chair Lina Khan.

Tesla’s driver assistant system has gained attention after some notable crashes. The National Highway Traffic Safety Administration announced a probe on Aug. 16 that had identified 11 crashes since early 2018 in which a Tesla using Autopilot crashed with vehicles involved in an emergency response situation.