Hyundai and Kia have been hit by a massive recall in the United States, which is estimated to cost both companies a few hundred million dollars.

Citing the plan submitted by both brands, which has to be approved by authorities, Reuters reports that approximately 1.3 million vehicles are involved in this safety campaign, on this side of the pond alone.

Affected are the Kia Optima, Sorento and Sportage, along with the Hyundai Sonata and Santa Fe, which have metal debris in the crankshaft that could cause serious damage to the unit’s components, leading to a possible engine stalling.

Any questions starting with ‘when’ and ‘how’ have yet to be answered, as this is the only data available for the United States so far, but a response could come soon from South Korea, as the two automakers are also recalling 171,348 million vehicles in their homeland, due to a similar problem.

The list includes the Kia K5, K7 and Sportage, and the Hyundai Sonata and Grandeur, all of which are powered by the 2.0-liter or 2.4-liter Theta 2 gasoline engines, produced before August 2013, as the local transport ministry said.

The report added that the latest recall is similar to the one announced in 2015, when nearly half a million Sonatas were called back in the US and South Korea to replace faulty engine parts.

However, the two companies denied the report in a statement: “The recall is related to a manufacturing process problem, not the structural problem of the Theta 2GDi engines, and we have completed improvements through appropriate measures.

Once the safety campaign kicks off on May 22 in Korea, dealers are expected to replace the defective engines with new ones, after inspection.

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