The National Highway Traffic Safety Administration (NHTSA) has launched a new engineering analysis investigation covering more than 3 million Hyundai and Kia models between the 2011 and 2016 model years.

The South Korean car manufacturers have been dealing with fire issues since September 2015 when its first engine fire recall was announced. A further eight engine recalls have been issued in the years since.

The NHTSA has opened its engineering analysis to evaluate whether previous recalls covered enough vehicles, while ABC News notes that the investigation could lead to more recalls. The agency added that it will monitor the effectiveness of previous recalls “as well as the long-term viability of related programs and non-safety field actions being conducted by Hyundai and Kia.”

Read Also: Kia Recalls 295,000 Cars In U.S. Over Engine Fire Risks

“Hyundai has taken numerous proactive actions to address engine issues, including conducting several recalls, launching a new engine monitoring technology, providing extended warranties and enhancing our customer service response,” the car manufacturer said in a statement. “Hyundai fosters a culture of transparency and accountability as the safety of our customers is the top priority in everything we do.”

Involved in previous recalls have been Hyundai and Kia models equipped with Theta II GDO, Theta II MPI, Theta II MPI hybrid, Nu GDI, and Gamma GDI engines. In November 2020, Hyundai and Kia were ordered to pay $137 million in fines and for safety improvements after moving too slowly in issuing a recall of over 1 million vehicles.

Kia has not yet commented on the NHTSA’s latest investigation.