Toyota Motor Corp. said a partial review of complaints of unintended acceleration after vehicles were repaired had found no evidence of failure in the electronic throttle system or the fixes.

Toyota, which has recalled more than six million vehicles in the US due to loose floor mats that can jam the accelerator and gas pedals that do not spring back as designed, said this week that it has fixed more than one million cars.

However, US regulators said they are reviewing more than 60 complaints that fixes made on the recalled vehicles had not solved the problem.

"It may be difficult to find out whether there are really problems with the cars or not. It may take time to settle the dispute," said Koji Endo, auto analyst at Advanced Research Japan. "I am afraid Toyota's brand may be further damaged if it is sued by one customer after another." The US sales unit of the world's largest automaker said in a statement that it had evaluated the cars and interviewed their owners and found no evidence of problems with the electronic throttle that some customers and regulators suspect could play a part in some incidents of unintended acceleration.

It also said no problems had been detected in the brake override system.

The announcement came at a time when Toyota's key executives delivered speeches to workers and dealers at the automaker's headquarters in Toyota City on Friday.

Toyota's North American chief Yoshimi Inaba told an audience of about 2,000 people that the automaker had not been able to dispel concerns about quality during a series of US congressional hearings.

"Toyota will review its organisation in North America and will promote information disclosure," said Mr Inaba.

Toyota also plans to review its research and development processes and set up a special team to beef up road tests, said technology chief Takeshi Uchiyamada, adding that the company was not able to get a good grasp of specific details of complaints about its cars.

Employees expressed concerns about a loss of skills on the factory floor.