WASHINGTON (Reuters)—U.S. regulators on Thursday said they were reviewing more than 60 complaints that fixes made on recalled Toyota Motor Corp. vehicles for unintended acceleration had not solved the problem.

The National Highway Traffic Safety Administration said in a statement it was reviewing the complaints and interviewing vehicle owners. The agency stressed that the complaints are unproven allegations.

The agency has also asked Toyota to provide information about any complaints it has received.

Toyota said on Wednesday after NHTSA reported the first 10 complaints that it, too, would move quickly to investigate the matter. The automaker said its recall remedies were rigorously tested.

NHTSA Administrator David Strickland said on Thursday that regulators were "determined to get to the bottom" of complaints. Transportation Secretary Ray LaHood told a Senate committee earlier in the day Toyota owners should bring their cars back to dealers if they are still having problems.

The government said it has the authority to order Toyota to provide a different solution if it appears that remedies are not working. NHTSA did not object to the company's recall fixes.

Toyota said this week it had fixed more than 1 million of the more than 6 million cars and trucks subject to recalls in October 2009 and January. Recalls covered loose floor mats that can jam the accelerator and gas pedals that do not spring back as designed.

NHTSA is reviewing whether there are glitches with Lexus and Toyota electronic throttles as a possible explanation for unintended acceleration.

Toyota, which has hired an independent consulting firm to study the issue, has said it has tested the systems exhaustively and found no problems. Congress has sharply criticized NHTSA for its handling of previous complaints about electronic throttles.

Separately, Edmunds.com, an online research source for consumers, said Toyota's newly unveiled purchase incentives including interest-free loans and free maintenance have noticeably boosted interest in the company's vehicles among prospective buyers. Kelley Blue Book also noted a spike in traffic for Toyota.