WASHINGTON (Reuters) - More than 65 percent of 46.2 million recalled Takata Corp 7312.T airbag inflators in the United States have not been repaired, a U.S. senator said on Thursday, urging automakers to speed up the pace of repairs.

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Senator Bill Nelson of Florida said only 15.8 million inflators out of 46.2 million inflators recalled to date have been repaired through mid-May, though nationwide recalls began in 2015. He was citing answers submitted from a National Highway Traffic Safety Administration (NHTSA) independent monitor.

About 8.8 million owners had received recall notices, Nelson said, but they were told no replacement parts were currently available.

The affected Takata inflators can explode with excessive force, unleashing metal shrapnel inside cars and trucks. They have been blamed for at least 16 deaths and more than 180 injuries worldwide.

Inflator recalls began around 2008 and involve around 100 million inflators around the world used in vehicles made by 19 automakers, including Honda Motor Co 7267.T, Ford Motor Co F.N, Volkswagen AG VOWG_p.DE and Tesla Inc TSLA.O.

Takata spokesman Jared Levy said the company “has dramatically increased the production of airbag replacement kits.” Takata has shipped over 26 million replacement kits, two-thirds of which include inflators manufactured by other suppliers, Levy said.

Last month, four automakers involved in the recalls agreed to a $553 million settlement covering owners of nearly 16 million vehicles with Takata airbag inflators, and agreed to take new steps to encourage owners to get recall repairs made.

Toyota Motor Corp’s 7203.T share of the settlement costs is $278.5 million, followed by BMW AG BMWG.DE at $131 million, Mazda Motor Co 7261.T at $76 million and Subaru Corp 7270.T at $68 million.

Nelson noted the administration of President Donald Trump still had not nominated a candidate to lead NHTSA.

“We’re in desperate need of a leader who will commit to resolving this Takata mess,” Nelson said in a statement.

In February, Takata pleaded guilty to U.S. charges of criminal wrongdoing and to pay $1 billion to resolve a federal investigation into its inflators.

The majority of the air bag-related fatalities and injuries have occurred in the United States, and most of them in Honda vehicles.

Automakers have recalled 46 million Takata air bag inflators in 29 million U.S. vehicles. By 2019, automakers will recall 64 million to 69 million U.S. inflators in 42 million total vehicles, NHTSA said in December.

Takata has been searching for more than a year for a financial sponsor to pay the replacement costs for its inflators which are at the center of the auto industry’s biggest recall.