Tesla CEO Elon Musk, under pressure after a sudden run of accidents and a rumoured SEC investigation into what the company knew about them and when, moved to soothe investors' fears by promising a new "masterplan" for the company as early as this week.

For the third time in as many weeks, reports emerged Monday of a Tesla vehicle that got into an accident while the car's self-driving feature was engaged.

Police in Montana say a Tesla got into an accident over the weekend in which the driver claims his car was in self-driving mode. That comes on the heels of a similar incident in Pennsylvania earlier this month, and a high-profile case in which a driver in Florida was killed in his vehicle with the self-driving mode engaged after a crash with a transport truck in May.

In addition to the expected transportation authorities, stock regulator the Securities and Exchange Commission is now looking into that crash, the Wall Street Journal reported Monday. It's investigating whether or not the company adequately disclosed to investors what it knew about that fatal incident, and when.

The fatal crash happened on May 7. Just over 10 days later, the company raised $2 billion US worth of new investment via a stock sale, and the filings related to it made no mention of the incident.

But the SEC has made no official comment on the matter — The Wall Street Journal cited an unnamed person familiar with the matter in its story about the investigation.

Tesla put out a statement to the media indicating it had "not received any communication from the SEC regarding this issue."

Yet Musk has been openly talking about the incident, and extolling the Tesla's pristine safety record.

"Model S had the lowest probability of injury of any car ever tested by NHTSA [the National Highway Traffic Safety Administration]," he said.

He has tried to shift the focus back to the company's future, by cryptically promising more details of the company's "masterplan" as early as this week.

The last time he touted such a plan was in 2006, when he laid out the company's long-term goals. They included production of a sports car — which became the company's roadster — and to build an affordable mass market car — which became the Model 3, set to come out next year for under $35,000 US.

The rest of the master plan from 2006 consisted of delivering vast improvements to battery technology, and to create "zero emission electric power generation."