But the news from the National Highway Traffic Safety Administration appears unrelated to the federal probe into Model S fires -- a safety issue that has dinged Tesla stock in recent months.
In fact, Tesla ( also said that it is still "awaiting feedback from NHTSA regarding their investigation of recent fire incidents." )
Tesla remains one of the hottest stocks of the year, up more than 350%, but it had lost momentum during the past few months due to a series battery fires.
Even though Tesla CEO Elon Musk reassured investors that there was "no reason for a recall," the stock tumbled more than 40% through October and November.
The stock has gained some ground in December, but is still 20% below it all-time highs.
In November, federal investigators started a probe into the fire risk for a Tesla Model S and have yet to release their findings.
The NHTSA reaffirmed Tesla's 5-star safety rating late Monday. While the safety rating is important, it is based on crash tests -- not fires.
The agency has not replied to a request for comment. Tesla declined to elaborate on its statement.
Some traders on StockTwits, a social investing site, pointed out what they saw as misguided enthusiasm.
"$TSLA goes up on a months-old safety rating that was 'reiterated,'" said BullHorns. "Every company should reiterate positive news daily. LOL."
StockTwits user Fiftyfifty said that investors may be overreacting: "Knew people would confuse these ratings with the unrelated & ongoing investigation."
Tesla, in its press release, said it is "worth noting that a Tesla vehicle is over five times less likely to experience a fire than the average gasoline car and that there have been zero serious injuries or deaths for any reason ever, fire or otherwise, in a Model S."
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