(Reuters) — The National Highway Traffic Safety Administration said Wednesday that an eighth U.S. death is linked to a faulty Takata airbag inflator, marking the first reported death since April and the ninth worldwide.

The auto safety agency also said it named a former U.S. Justice Department official to oversee the massive recalls of airbags and the Japanese parts firm's compliance with a settlement.

NHTSA spokesman Gordon Trowbridge told reporters on a conference call that the new death took place in July in a recalled used 2001 Honda Accord coupe near Pittsburgh. The unidentified teen-aged driver was hospitalized after a Takata airbag ruptured and died several days later.

Sources close to the matter said the death involved a 13-year-old boy who was in an early morning crash after he apparently took the keys without permission from a parent and got behind the wheel.

Trowbridge said Honda, Fuji Heavy Industries Ltd.'s Subaru unit, and Mazda Motor Corp. will add an estimated "few hundred thousand vehicles" to the massive recall campaigns based on additional inflator testing and that others may as well.

The expanded recalls for passenger side inflators include the 2005-2008 Mazda6, 2003-2004 Honda CR-V and 2005-2008 Subaru Legacy and Outback. Honda said it was adding 127,000 vehicles.

Takata's inflators can explode with too much force and spray metal shrapnel into vehicle passenger compartments and are linked to nine deaths and more than 100 injuries.

All of the nine deaths, including the death of a pregnant woman in Malaysia, have been in Honda vehicles.

Reuters reported earlier civil suits involving most airbag deaths have been settled by Takata and Honda.

Honda said it is working to determine the cause of the death. The company said the prior owner first got a recall notice in 2010. Honda said it mailed a new recall notice on July 21, one day before the crash.

NHTSA said a quarter of vehicles recalled have been fixed, including a third of vehicles in high-humidity areas, where automakers believe the risk is highest for ruptures. But that still leaves around 15 million vehicles unrepaired.

NHTSA said it named John Buretta, a former official in the Justice Department's criminal division, to serve as independent monitor overseeing the Takata recalls.

Takata said in a statement the Mr. Buretta "would have our full cooperation and support."

Sens. Edward Markey, D-Mass., and Richard Blumenthal, D-Conn., praised the appointment but said it is "largely required because NHTSA has moved too slowly and ineptly for years, allowing a patchwork of recalls." They also want all vehicles with possibly defective airbags recalled.

In November, Takata agreed to pay a $70 million fine for safety violations and could face deferred penalties of up to $130 million under a NHTSA settlement.

The monitor will help regulators oversee one of the biggest and most complex safety recalls in U.S. automotive history, encompassing 23 million air bag inflators in 19 million vehicles manufactured by 12 car companies.