WASHINGTON (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.

In a letter to Ford made public 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."