Tesla said it is recalling 3,470 Model Y vehicles in the US owing to concerns that bolts in the second-row seat back frames may not have been securely tightened.

In a regulatory filing with The National Highway Traffic Safety Administration (NHTSA), the electric vehicle maker said the loose bolts may reduce the performance of the seat belt system, and increase injury risks in the case of a car crash.

Tesla estimates that 4% of the recalled cars have the defect, which the company says it identified on December 10, when an operator in Tesla’s Fremont, California facility noted that the second-row seats, had not been properly screwed in.

The EV maker said it had identified five warranty claims it has received since the discovery that might stem from the insecure bolts, and that it was not aware of any injuries or deaths relating to the recall reason.

Tesla said that it will inspect the bolts on recalled vehicles and “if necessary retorque them to specifications.” The company added it does not plan to issue any reimbursements because there are “no warranty repairs related to these conditions.”

The carmaker added that a supplier implemented improved process controls together with improved training and supervision in a bid to ensure bolts are properly tightened.

Last month, Tesla issued a voluntary recall on 362,758 vehicles that had already received or were due a software update for the carmakers’ Full Self-Driving (FSD) feature, which the company says may cause the vehicles to disobey local traffic laws and increase the risk of a crash.

According to the NHTSA, this issue affects select vehicles across all Tesla models: the Model S, Model X, Model 3, and Model Y.