The probe comes two months after the electric vehicle maker run by Elon Musk started a self-driving taxi service in Austin, Texas, with hopes of soon offering it nationwide. The company also hopes to send over-the-air software updates to millions of Teslas already on the road that will allow them to drive themselves.
Investors enthusiastic about such plans have kept Tesla stock aloft despite plunging sales and profits due to boycotts over Musk's support for U.S. President Donald Trump and far-right politicians in Europe.
The safety agency said the probe will focus on why Tesla took so long to report the crashes, whether the reports included all the necessary data and details and if there are crashes that the agency still doesn't know about.
Tesla did not respond to a request for comment, but the agency noted that the company has told it the delays were “due to an issue with Tesla’s data collection," which Tesla says has now been fixed.
The new investigation follows another probe that began in October into potential problems with Tesla's self-driving technology in foggy weather and other low visibility conditions, which has led to several accidents including one death. That probe involves 2.5 million Tesla vehicles.
Tesla stock fell nearly 1% in midday trading Thursday to $321.