Hyundai and Kia are recalling over 500,000 vehicles as both companies continue to be investigated by the federal government.

The largest individual recall involves about 380,000 Kia Soul vehicles from 2012 to 2016 with 1.6-liter engines. According to National Highway Traffic Safety Administration documents, high exhaust gas temperatures can cause damage to the catalytic converter, which can result it "abnormal engine combustion. "

Kia also issued two other recalls, one for certain 2015-2018 Sedona vehicles with faulty occupant detection system wiring harnesses, and another for some 2011-2012 Kia Sportage vehicles with potential engine oil pan leakage.

Meanwhile, Hyundai is recalling 120,000 Tucson vehicles from 2011 to 2013 due to potential engine oil pan leakage. If not addressed, the loss of oil may result in engine damage.

The National Highway Traffic Safety Administration began investigating Kia and Hyundai in 2017 to find out if the automakers moved quickly enough in recalling over 1.6 million vehicles because of engines stalling. Last year, the NHTSA expanded probes into Hyundai and Kia engine failures to include complaints about fires in the automakers' vehicles.

Following a recall in January, each automaker promised to do a “product improvement campaign” that covers a total of 3.7 million vehicles to install software that will alert drivers of possible engine failures and send the cars into a reduced-speed “limp” mode if problems are detected.

Hyundai and Kia did not immediately respond to USA TODAY's request for comment.