The US National Highway Traffic Safety Administration (NHTSA) has said that new testing is prompting Takata to declare 2.7m more airbag inflators defective.

The company filed documents with the NHTSA adding 2.7m vehicles to the recall from Ford, Nissan and Mazda, all with a type of inflator that previously was thought to be safe.

The NHTSA said in a statement that tests done by Takata show that for the first time, a type of desiccated inflator "will pose a safety risk if not replaced." The agency says it has no reports of any inflators with the desiccant rupturing. The NHTSA said that not all Takata inflators with a desiccant are being recalled. Takata used different drying agents in other inflators, the agency said.

Nissan said the new recall affects just over 515,000 Versa subcompact hatchback and sedans from the 2007 through 2012 model years. Mazda said its recall covers about 6,000 B-Series trucks from 2007 through 2009. Ford, which has the most vehicles involved in the latest recall, is reviewing the information and will file a list of models within the five days required by law.

Reuters reported that Ford spokesman John Cangany said the issue covers about 2.2m Ford vehicles.

Over 70m Takata airbag inflators are or will be under recall in the US by 2019, in the largest and most complex auto safety recall in US history.