NEW YORK (TheStreet) -- Shares of Tesla Motors (TSLA) are gaining 1.48% to $219.99 in pre-market trading Monday after CEO Elon Musk tweeted yesterday that he is working on the second part of his "top secret Tesla masterplan" and hopes to publish it later this week.

The tweet comes amid investigations into two crashes of Tesla cars and ongoing questions related to Musk's plan to acquire solar panel company SolarCity (SCTY).

On July 1, a Tesla Model X crashed into a turnpike guard rail in Pennsylvania. The National Highway Traffic Safety Administration (NHTSA) said last week it is investigating the accident "to determine whether automated functions were in use at the time of the crash," Reuters noted.

Tesla has said it has no reason to believe its "Autopilot" function had anything to do with the crash.

The accident comes after a fatal crash in Florida on May 7 involving its Autopilot mode.

Separately, TheStreet Ratings Team has a "Sell" rating with a score of D+ on the stock.

The company's weaknesses can be seen in multiple areas, such as its deteriorating net income, generally high debt management risk, disappointing return on equity, weak operating cash flow and generally disappointing historical performance in the stock itself.

Recently, TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this articles's author.

You can view the full analysis from the report here: TSLA