Tesla Motors, the maverick electric-car maker, is under scrutiny from federal regulators over suspension failures attributed to its biggest-selling model — along with reports that it had asked owners not to disclose the problem.

The nation’s top auto safety regulator, the National Highway Traffic Safety Administration, said on Thursday that at least some Tesla customers who experienced suspension failures with Model S luxury cars were asked to sign confidentiality agreements about the issue.

“The agency immediately informed Tesla that any language implying that consumers should not contact the agency regarding safety concerns is unacceptable, and N.H.T.S.A. expects Tesla to eliminate any such language,” said Bryan Thomas, an agency spokesman. “Tesla representatives told N.H.T.S.A. that it was not their intention to dissuade consumers from contacting the agency.”

The regulator added that the agreements that Tesla required were “troublesome.”

Tesla did not respond Thursday to requests for comment. [On Friday, the company responded in a blog post, saying there was no safety defect with the Model S nor any intent to discourage complaints to regulators.]