US safety officials have opened an investigation into complaints of steering problems in Toyota's Corolla, the world's best-selling car, a government source said Wednesday.
"We're opening an investigation into the 2009 and 2010 Toyota Corolla for steering issues," a Transportation Department official told AFP on condition of anonymity.
Up to 500,000 vehicles could be affected, as long as the investigation is not widened abroad or beyond the 2009 and 2010 models, according to the official.
The Japanese giant said earlier that it was considering recalling the Corolla models over the steering problems.
The 2009-2010 Corolla is among the models involved in Toyota's earlier recalls of millions of vehicles worldwide to fix problems with unintended acceleration.
Toyota also announced it would fit all new models with a system to cut engine power when the driver steps on the accelerator and brake pedals at the same time, to prevent runaway car crashes blamed for dozens of deaths.
If there is a defect in the Corolla that affects safety, "we will start recalls," Toyota executive vice president Shinichi Sasaki told reporters. "We are in the process of investigating."
An AFP examination of complaints lodged with US safety officials found that 110 Corolla drivers reported steering problems in 2009 and 53 so far this year.
The total number of complaints lodged by Corolla owners reached 266 in 2009 and 115 so far this year.
US authorities said this month they were reviewing dozens of complaints about the Corolla -- the world's most popular car ever, with total global sales of more than 30 million since the first version was launched in the 1960s.
There have been reports of the vehicle unexpectedly veering off course at speeds above 40 miles (64 kilometers) per hour.
In an effort to restore confidence in its brand, Toyota said its president Akio Toyoda would head a task force to improve quality control and enable the group to respond more quickly to reports of defects.
But the Toyota family scion, under fire for his handling of the safety problems, signaled he would miss a grilling by US lawmakers next week on the mass recalls, sending one of his top North America executives instead.
"I am sure they are well equipped to respond well to the questions," he told a news conference, his third this month on the safety issues that have tarnished the company's once-glowing reputation.
US authorities on Tuesday demanded that the world's largest carmaker hand over documents to prove it did not drag its feet in recalling the vehicles once it learnt about defects that can lead to unintended acceleration.
Investigators will probe how and when the manufacturer discovered the problems in the recalled Toyota and Lexus vehicles, the National Highway Traffic Safety Administration (NHTSA) said.
President Barack Obama's Transportation Secretary Ray LaHood has vowed "to hold Toyota's feet to the fire" to make sure its cars are safe, but Toyoda denied his company had ever covered up safety defects.
"We have not withheld information and we shall not do so in the future," said Toyoda, the grandson of the company's founder.
The Japanese giant, which in 2008 dethroned General Motors as the world's biggest automaker, has pledged to fix more than eight million vehicles worldwide, more than its entire 2009 global sales, due to the safety problems.
