Auto safety regulators in the United States have initiated an investigation into 16 separate recalls by Hyundai and Kia, encompassing 6.4 million vehicles, due to concerns about brake fluid leaks that pose a risk of fires. The recalls, dating back to 2016, address issues related to the antilock braking system and Hydraulic Electronic Control Units (HECU), both sourced from the same supplier.

The National Highway Traffic Safety Administration (NHTSA) announced the audit query on Monday, focusing on evaluating the timeliness of the defect decision-making process by Hyundai and Kia, adherence to reporting requirements, and understanding the variations in defect descriptions and remedies across the recalls.

Hyundai and Kia, South Korean automakers, have faced ongoing challenges with recalls, particularly concerning brake fluid leaks that may lead to electrical shorts and, subsequently, fires. The NHTSA's investigation seeks to assess the overall handling of these recalls by the automakers.

As of Monday, Hyundai and Kia had not responded to requests for comments regarding the ongoing investigation.

In September, the automakers recalled a combined total of 3.37 million vehicles in the United States due to the risk of engine fires, advising owners to park their vehicles outside and away from structures until necessary repairs were completed.

The recalls highlighted the potential for internal brake fluid leaks to cause electrical shorts, resulting in a heightened risk of fires. Hyundai reported 21 fires and 21 thermal incidents since 2017, while Kia confirmed at least 10 fires and melting incidents.

Kia specified that the Hydraulic Electronic Control Unit (HECU) in the affected vehicles might experience an electrical short due to brake fluid leaks, while Hyundai pointed to internal brake fluid leaks in the Anti-Lock Brake System (ABS) module, leading to electrical shorts.

The September recalls covered various models and model years, affecting a range of Kia and Hyundai vehicles. The investigation by the NHTSA reflects the ongoing scrutiny of safety concerns within the automotive industry and underscores the importance of timely and effective defect resolution.

(With Reuters inputs.)