In 2014, General Motors (GM) recalled 1.4 million 2009 through 2014 Chevrolet Traverse, GMC Arcadia, Buick Enclave, and Saturn Outlook vehicles for a seat belt issue. Since that time, the National Highway Traffic Safety Administration (NHTSA) has started an investigation into the effectiveness of the recall remedy.

The NHTSA has received four consumer complaints about the recall, which was initiated because there was a risk that the steel cable that connected the front seat belts to the vehicle could become separated, leading to injury if the vehicle were to crash.

According to the initial recall order, “In the affected vehicles, the flexible steel cable that connects the seatbelt to the front outboard seating positions may fatigue and separate over time. If the steel cable becomes fatigued and separates, the seat belt may not properly restrain the seat occupant increasing the risk of an injury in a crash.”

No reports of injury were provided in the consumer complaints, but rather in one instance the seat belt snapped upon fastening it even after having it fixed, according to the NHTSA website. To rectify the issue, GM dealers were instructed to examine the cables and make replacements as required on all affected vehicle models.

The NHTSA is now investigating the recall repair and will determine the next steps to take with the 1.4 million vehicles affected by the seat belt issue. GM said it would fully cooperate as well as support the investigation by the NHTSA, the Associated Press reported.

Shares of GM stock were down 4.18 percent as of 1:55 p.m. ET on Friday.