WASHINGTON, May 9 (Reuters) - A U.S. auto safety agency

said on Thursday it has "significant safety concerns" over Ford

Motor's ( F ) recall of more than 42,000 SUVs over concerns fuel

leaks could lead to an engine fire.

The National Highway Traffic Safety Administration (NHTSA)

said last month it was investigating the adequacy and safety

consequences of Ford's proposed recall remedy for 2022-2023

model year Bronco Sport and 2022 Ford Escape SUVs with 1.5L

engines.

The No. 2 U.S. automaker said a fuel injector may crack and

leak fuel, which could cause an underhood fire.

Ford has proposed an engine control software update and

installation of a drain. It is not proposing to replace the fuel

injectors that could crack.

In a letter to Ford made public on Thursday, NHTSA said

Ford's plan "does not address the root cause of the issue and

does not proactively call for the replacement of defective fuel

injectors prior to their failure," adding that the agency has

"identified significant safety concerns."

NHTSA is asking Ford to answer extensive questions about the

recall by June 21, including how it settled on the remedy.

Ford reiterated on Friday that it is working with NHTSA to

support the agency's investigation.

Ford said last month is aware of five underhood fires on

1.5L Escape and Bronco Sport vehicles in the new recall

population, but that it had no reports of accidents or injuries

tied to the issue.

The software update will detect a pressure drop in the fuel

rail, providing a "seek service" message to the driver and

disabling the high-pressure fuel pump, reducing engine power

output and lowering temperatures of possible ignition sources.

In 2022, Ford recalled nearly 522,000 2020-2023 Ford Escape

and 2021-2023 Ford Bronco Sport for the same issue with the same

remedy, NHTSA said.

Ford told NHTSA in late 2022 it had 54 reports alleging

underhood fires in 2020-2022 Bronco Sport and Escape vehicles,

equipped with the 1.5L engine in North America, along with

reports of four injuries in two incidents.