U.S. regulators said on Monday they could expand their investigation into Takata Corp (7312.T) air bag inflators beyond 11 automakers, as questions arose about whether vehicle design played a role in the devices posing a deadly risk to the public. National Highway Traffic Safety Administration (NHTSA) chief Mark Rosekind said his agency can add more auto manufacturers to the consent order that regulators announced with Takata in May. He said some car makers could also begin to move more quickly when they suspect a potential problem.