DETROIT -- Toyota's problems with runaway acceleration just won't go away.

The company said Friday that it will expand its recall of vehicles for unintended acceleration to include about 154,000 Lexus SUVs. Floor mats can trap the gas pedal and cause the vehicles to speed up without warning. U.S. safety regulators, who asked Toyota to recall the SUVs, said they may investigate whether the company reported the problem to them fast enough.

Toyota now adds the 2010 Lexus RX 350 and RX 450H to a string of embarrassing safety recalls that began three years ago. The Japanese automaker has recalled more than 14 million vehicles globally to fix problems including sticky gas pedals and floor mats. The recalls tarnished the company's sterling reputation for reliability and cut into sales.

In Canada, Toyota said its 2010 Lexus RX350 and RX450h models are affected including a total of about 14,500 vehicles.

The National Highway Traffic Safety Administration sought the Lexus SUV recall after reviewing complaints from customers and information from the company. The agency does not believe any additional Toyota vehicles have the same problem.

Toyota spokesman Brian Lyons said the company is co-operating with NHTSA and provided information in a timely manner after investigators asked for it.

If NHTSA decides to open an investigation, it wouldn't be the first dustup between Toyota and the agency. In 2010 and 2011, Toyota paid the government a record $48.8 million in fines for failing to promptly alert regulators to safety problems.

Owners of the Lexus SUVs should take out the driver's side floor mat and have their vehicles serviced as quickly as possible, NHTSA said.

They will be notified of the problem by mail in early August, and dealers will fix it for free, Toyota said. Although Toyota is still developing a plan to fix the problem, it will include replacement of the gas pedal.

Experts say if your car accelerates unexpectedly, you should step on the brake and shift into neutral, steer safely to the roadside and shut off the engine.

The automaker's string of unintended acceleration recalls occurred in 2009 and 2010, raising suspicions about Toyota's electronic throttle controls. NHTSA brought in scientists from NASA to help investigate, finding nothing wrong with the electronics in a probe that ended early in 2011. NHTSA said at the time recalls for sticky gas pedals and floor mats would take care of unintended acceleration.

Although Friday's recall comes nearly three model years after the Lexus SUVs were introduced, a NHTSA spokeswoman said the agency had no data to seek a recall before that.

When NHTSA closed its Toyota unintended acceleration probe in 2011, there were no complaints about the RX 350 from model years 2008 and 2009, and only three complaints from the 2010 model year, agency spokeswoman Lynda Tran said. There also were no complaints about the RX 450 H gas-electric hybrid.

But government investigators noticed an increase in consumer complaints about the Lexus SUVs late last month, and it asked Toyota about the problem. Last week, Toyota told the agency that it had a ``significant volume'' of complaints about the same issue, so NHTSA asked for the recall, the agency said in a statement.

Now, NHTSA has asked Toyota for more documentation to see if the company ``met its obligation to notify the agency and conduct a recall in a timely manner,'' NHTSA's statement said.