South Korean automaker Hyundai is recalling 140,000 vehicles in the United States and Puerto Rico because of an air bag problem, according to documents filed with US auto safety regulators. There were no known accidents or injuries as a result of this problem, the company said in its recall notice to the National Highway Transportation Safety Administration. The issue relates to the bolts that attach the driver's airbag to the steering column in Hyundai's Tuscon compact sport utility vehicles. "During assembly, it is possible that the two bolts attaching the driver's airbag module to the steering wheel assembly were not properly tightened," the automaker wrote in its letter to the NHTSA. "If both bolts become loose and detach, the driver's airbag module could become detached from the steering wheel." Hyundai said the defect "could result in injury in the event of a crash." The automaker said it was recalling 137,500 vehicles in the United States and 3,500 in Puerto Rico, from model years 2011 to 2014. The issue came to Hyundai's attention in December 2013, after reports of dealership service departments tightening the bolts under warranty. The automaker will ask owners to bring their vehicles to have the bolts checked. On Friday, the NHTSA imposed a record $35 million fine on US auto giant General Motors for its failure to promptly recall cars with ignition faults linked to at least 13 deaths.