The request for an investigation adds to a growing list of safety-related problems for Toyota, the world's top-selling automaker.Earlier this month the company said it would pay $29 million to 29 states and American Samoa as part of a settlement related to its safety recalls. State attorneys general sued Toyota in 2010 after it recalled 14 million vehicles globally for accelerating without warning. The lawsuit accused Toyota of failing to notify customers promptly about the problems. During their investigation, the attorneys general found that poor communication between Toyota's headquarters in Japan and its U.S. operations had contributed to the problem. Toyota has promised to improve communications and give its U.S. executives more decision-making power. Toyota Motor Corp. has blamed sticky gas pedals, faulty floor mats and driver error for the acceleration issue. The National Highway Traffic Safety Administration and NASA have both investigated and agreed with Toyota that electronics weren't causing the problem. Toyota has paid more than $1 billion to settle claims related to the recalls, including a record $17.4 million fine to the U.S. government for failing to quickly report safety problems. It continues to negotiate individual cases, including an undisclosed settlement reached last month with the families of two people who were killed when their Toyota Camry slammed into a wall in Utah in 2010.