The U.S. National Highway Traffic Safety Administration is demanding volumes of information from the automaker as it investigates the fix in a March 8 recall of nearly 43,000 Bronco Sport SUVs from the 2022 and 2023 model years, and Escape SUVs from 2022. All have 1.5-liter engines.

Ford says the SUVs have fuel injectors that will crack, allowing gas or vapor to leak near hot engine parts that can cause fires, fuel odors and an increased risk of injuries.

In an April 25 letter to Ford released Thursday, the agency’s Office of Defects Investigation wrote that based on its review of the recall repairs, it “believes that the remedy program 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.”

Ford’s remedy for the leaks is to add a drain tube to send the gas away from hot surfaces, and a software update to detect a pressure drop in the fuel injection system. If that happens, the software will disable the high pressure fuel pump, reduce engine power and cut temperatures in the engine compartment. Owners also will get a “seek service” message.

But in the 11-page letter to the automaker, the agency asks Ford to detail any testing it did to verify the remedy resolved the problem and whether hardware repairs are needed. It also asks the company to explain any other remedies that were considered and any cost-benefit analysis the company did when it picked the fix.

Safety advocates have said Ford is trying to avoid the cost of replacing the fuel injectors and instead go with a cheaper fix that drains gasoline to the ground.

Ford said Thursday that it is working with the NHTSA during its investigation.

NHTSA also is asking ford to detail how the software will detect a fuel pressure drop, how much time elapses between cracking and detection, and what messages will be sent to the driver. It also asks what effect disabling the high-pressure fuel pump has on other fuel system parts, and how the SUVs will perform when the pump is disabled.

The agency also wants to know how much fuel will leak and whether the amount complies with federal environmental and safety standards. And it wants to hear Ford’s take on “its obligations (legal, ethical, environmental and other) to prevent and/or limit fuel leakage onto the roadway at any point during a vehicle’s lifespan.”

Ford has to provide information to the agency by June 21, the letter said. Depending on the results of its investigation, the agency can seek additional repairs that fix the fuel leaks.

The company has said in documents that it has reports of five under-hood fires and 14 warranty replacements of fuel injectors, but no reports of crashes or injuries.

In a previous email, Ford said it is not replacing fuel injectors because it is confident the recall repairs “will prevent the failure from occurring and protect the customer.” The new software triggers a dashboard warning light and allows customers to drive to a safe location, stop the vehicle and arrange for service, the company said. NHTSA documents filed by Ford say the problem happens only in about 1% of the SUVs.

The company also said it will extend warranty coverage for cracked fuel injectors, so owners who experience the problem will get replacements. Repairs are already available, and details of the extended warranty will be available in June, Ford said.

The recall is an extension of a 2022 recall for the same problem, according to Ford. The repair has already been tested on vehicles involved in the previous recall, and Ford said it’s not aware of any problems.

The company also said it isn’t recommending that the SUVs be parked only outdoors because there’s no evidence that fires happen when vehicles are parked and the engines are off.

NHTSA said in documents that in the 2022 recall, which covered nearly 522,000 Bronco Sports and Escapes, Ford had the same remedy as the latest recall.