DETROIT — U.S. auto safety regulators said Monday they are monitoring data from a group of mostly unrecalled Takata air bag inflators after one of them exploded in a BMW and hurled metal fragments that seriously injured a driver in Chicago.The National Highway Traffic Safety Administration has been investigating the batch of about 30 million inflators since 2021 to see if they exhibit the same traits that forced Takata to recall 67 million of the devices since 2001.On Saturday, the agency posted documents showing …