U.S. auto safety investigators are reviewing reports of suspension problems in Tesla Motors' Model S cars, a government spokesman said on Thursday.
Bryan Thomas, a spokesman for the National Highway Traffic Safety Administration, said the agency is "examining the potential suspension issue on the Tesla Model S, and is seeking additional information from vehicle owners and the company."
A review is a step before the agency decides whether to open a formal investigation leading to a potential safety recall.
The NHTSA also said it had learned that Tesla had entered into what it called a "troublesome nondisclosure agreement" with a Tesla Model S owner who had suspension problems.
A Tesla spokeswoman said she was looking into NHTSA's statement, declining to immediately elaborate.
Shares of Tesla Motors hit session lows after the news. Shares of Tesla closed down 2.6 percent at $229.36 on the Nasdaq.
A website that writes about auto issues, dailykanban.com, reported on owner complaints earlier this week that focus on a possible defect in Tesla Model S vehicles that may cause suspension control arms to break, which could cause the driver to lose control of the car.
The site linked to a Model S owner who wrote on a Tesla fan website that said he had suspension problems and had received an email from an NHTSA investigator.
The owner said Tesla agreed to pay 50 percent of a $3,100 repair bill if the owner agreed to keep confidential the arrangement.
NHTSA said Thursday it "learned of Tesla's troublesome nondisclosure agreement last month. The agency immediately informed Tesla that any language implying that consumers should not contact the agency regarding safety concerns is unacceptable, and NHTSA expects Tesla to eliminate any such language."
The agency said Tesla "told NHTSA that it was not their intention to dissuade consumers from contacting the agency. NHTSA always encourages vehicle owners concerned about potential safety defects to contact the agency."
— CNBC.com contributed to this report.