NHTSA's Office of Defects Investigation said it had received 50 complaints alleging such failures on Fusion and MKZ vehicles from the 2013-18 model years and was aware of one crash allegedly related to the issue.
Many of the complaints claim "the brake hoses are rupturing, leaking brake fluid and occurring with little to no warning," according to a report released Friday.
Front brake hose ruptures and leaking brake fluid can result in increased stopping distances, the agency said.
Ford Motor Co. did not immediately respond to a request for comment.
In August 2020, Ford recalled more than 488,000 2015-18 Ford Edge and 2016-18 Lincoln MKX vehicles because the front brake hoses on the midsize crossovers may rupture prematurely.
The agency has launched the investigation — known as a "recall query" — for further assessment and to determine whether more vehicles should be recalled.
With a safety probe, the agency will assess the scope and severity of the potential defect and other possible safety-related issues.
Most NHTSA investigations start as preliminary evaluations, in which agency engineers request information from the manufacturer, including data on complaints, injuries and warranty claims. The manufacturer also can present its view regarding the alleged defect and may issue a recall.
After the evaluation, NHTSA will either close the investigation or move into the next phase. If a safety-related defect exists, according to NHTSA, the agency might send a "recall request" letter to the manufacturer.