The U.S. Department of Transportation said Tuesday it demanded documents related to Toyota's massive recalls in the United States to find out if the Japanese automaker acted quickly enough. The legal documents demand that Toyota tell the government when and how the company learned of the safety defects in millions of vehicles over accelerator pedals. The documents were delivered to Toyota on Tuesday, and the company must respond within 60 days or be fined. The department's National Highway Traffic Safety Administration (NHTSA) said it was using its authority to obtain the documents “to determine if the automaker conducted three of its recent recalls in a timely manner.” The agency noted that U.S. law requires all automakers to notify it within five days of determining that a safety defect exists and promptly conduct a recall. “Safety recalls are very serious matters, and automakers are required to quickly report defects,” Transportation Secretary Ray LaHood said in a statement. Specifically, the NHTSA said it “is requiring Toyota to provide documents showing when and how it learned of the defects affecting approximately 6 million vehicles in the U.S. alone.” Investigators will probe how the company learned of the defects, such as via consumer complaints or factory testing, it said. “Investigators are also looking into whether Toyota discovered the problems during pre-production or post-production of the affected vehicles.” The intensifying government investigation of Toyota and new production stoppages at its U.S. assembly plants were more consequences of the recall of 8.5 million vehicles by the world's biggest automaker. Toyota faces separate investigations by the Obama administration and Congress as it struggles to maintain its loyal customer base and its reputation for safety and quality.