On Monday, the U.S. National Highway Traffic Safety Administration (NHTSA) announced that it is elevating its investigation involving 129,222 Ford Motor vehicles related to incidents with the company’s hands-free driving feature, BlueCruise.

The inquiry began after reports of two fatal accidents in April involving Ford Mustang Mach-E vehicles that were equipped with BlueCruise technology.

The agency is advancing its investigation to an engineering analysis, which includes models from the years 2021 to 2024.

An engineering analysis is a necessary step before the NHTSA can issue a recall.

The BlueCruise system utilizes a camera-based driver monitoring feature to assess if the driver is paying attention, and it operates on nearly all highways in the U.S. and Canada that do not have intersections or traffic signals.

This technology was first introduced in the 2021 model year and is currently offered in a limited selection of Ford and Lincoln models.

In April, the National Transportation Safety Board (NTSB) launched separate investigations into the two Mach-E incidents, including a crash on February 24 in Texas involving a Honda CR-V and another accident on March 3 in Philadelphia.

According to the NHTSA, both fatal incidents occurred while the Mustang Mach-E was traveling over 70 mph on a highway at night in BlueCruise mode when it struck a stationary vehicle.

The agency noticed that these vehicles likely have system shortcomings regarding their ability to detect stationary vehicles while driving at highway speeds in low-light conditions.

The NHTSA stated that it will further explore these limitations and assess how well drivers can react in situations where these limitations are exceeded.

Ford has not yet provided a response to a request for comments from Reuters.