By David Shepardson

WASHINGTON (Reuters) – Kia Motors Corp and affiliate Hyundai Motor Co said on Thursday they are recalling around 534,000 additional U.S. vehicles at risk of engine fires.

Kia said it is recalling 378,000 2012-2016 Kia Soul vehicles over engine damage and fire risks, while Hyundai and Kia are recalling 155,000 2011-2013 Tucson vehicles and 2011-2012 Sportage vehicles over possible oil pan leaks in a separate callback.

Last month, the companies said they would recall 168,000 vehicles for fire risks.

The South Korean automakers have now recalled more than 2.3 million vehicles since 2015 to address various engine fire risks in a series of recalls.

In November 2018, Reuters reported that federal prosecutors had launched a criminal investigation into Hyundai and Kia to determine if vehicle recalls linked to engine defects were conducted properly. The companies have declined to comment on the probe.

In May 2017, the U.S. National Highway Traffic Safety Administration (NHTSA) opened a formal investigation into the recalls of nearly 1.7 million Hyundai and Kia vehicles over engine defects.

Hyundai said it met with NHTSA in December 2018 to discuss the company’s analysis and the agency informed the company that it “expected Hyundai to conduct a safety recall” of the 2011-2013 Hyundai Tucson.

There are no reports of accidents or injuries connected to either new recall, the companies said.

Kia said one new recall Thursday was prompted by high exhaust gas temperatures that may damage the catalytic converter and potentially other parts. Dealers will upgrade software to prevent overheating of the catalytic converter.

Reuters reported in January that the companies would offer software upgrades for 3.7 million vehicles not being recalled. The automakers said the software update aims to protect the vehicles from internal damage, and they will also offer new extended warranties for engine issues.

A South Korean whistleblower in 2016 reported concerns to NHTSA, which has been probing the timeliness of three U.S. recalls and whether they covered enough vehicles.

In 2015, Hyundai recalled 470,000 U.S. Sonata sedans, saying engine failure would result in a vehicle stall, increasing the risk of a crash. At the time, Kia did not recall its vehicles, which share the same “Theta II” engines.

In March 2017, Hyundai expanded its original U.S. recall to 572,000 Sonata and Santa Fe Sport vehicles with “Theta II” engines, citing the same issue involving manufacturing debris.

On the same day, Kia also recalled 618,000 Optima, Sorento and Sportage vehicles, all of which use the same engine.

On Wednesday, the Centre for Auto Safety, which has petitioned NHTSA to demand the recall of additional vehicles, told Congress that Kia and Hyundai must recall more vehicles at risk of fires after reports of 300 fires that were not the result of a collision.

(Reporting by David Shepardson; Editing by Phil Berlowitz)