Federal safety regulators said on Friday they had closed an investigation into whether the design of Tesla Motors’ all-electric car was making it prone to catch fire, after the automaker said it would provide more protection to its lithium-ion batteries.

The addition of a titanium underbody shield and aluminum deflector plates, along with increased ground clearance, “should reduce both the frequency of underbody strikes and the resultant fire risk,” the National Highway Traffic Safety Administration said on its website.

Tesla’s share price rose $5.05 on Friday, or 2.44 percent, closing at $212.37. It had fallen 2.7 percent on Thursday.

Twice last year in the United States, the Tesla Model S sedans burst into flames after running over debris.