The scandal engulfing Volkswagen AG, which has admitted cheating diesel vehicle emissions tests in the United States, spread east on Tuesday as South Korea said it would investigate three of the maker's diesel models.
Volkswagen shares plunged by 19 percent on Monday after the U.S. Environmental Protection Agency (EPA) said on Friday that the world's biggest carmaker by sales used software that deceived regulators measuring toxic emissions and could face penalties of up to $18 billion.
Media reports say the U.S. Department of Justice has started a criminal probe into the allegations, which cover several VW and Audi-branded diesel models including the Audi A3, VW Jetta, Beetle, Golf and Passat.
The South Korean probe will involve 4,000 to 5,000 Jetta, Golf and Audi A3 vehicles produced in 2014 and 2015, Park Pan-kyu, a deputy director at South Korea's environment ministry, told Reuters.
The ministry will consider recalling those vehicles after conducting the investigation, he said.
"If South Korean authorities find problems in the VW diesel cars, the probe could be expanded to all German diesel cars," he said.
Volkswagen Korea declined to comment.
German rivals Daimler and BMW have said the accusations against VW did not apply to them.
The European Commission has said it is in contact with VW and U.S. regulators, but it was too early to say whether VW vehicles in Europe were also affected.
A VW spokesman in Australia said the company had contacted its head office in Germany asking for advice about how to proceed and whether it expected cars sold in Australia to be affected. He added that the Australian office had not been contacted by local police or government agencies.
Overnight, VW's U.S. head Michael Horn, who was attending a lavish event in New York to promote the 2016 VW Passat, admitted the company had "totally screwed up" and vowed to make amends.
Horn's presentation did not promote the environmental efficiency of the Passat's "clean diesel" model, focusing instead on the vehicle's new sensor technology to assist with parking and avoiding accidents.
It is unclear what will be the ultimate cost of the scandal to VW, which also faces a class-action lawsuit from buyers, but sales of affected versions of the relevant models have already been suspended in the United States and Canada.
"I had to back out of a couple deals the same day," said a dealer attending Horn's event in New York. "That hurt me because we found out in real-time. What are you going to do?"
German Economy Minister Sigmar Gabriel has expressed concern that the scandal could damage "the justifiably excellent reputation of the German car industry", and South Korea, where two thirds of all car imports in the first half were diesel, could be a significant early gauge of customer response.
German car sales in South Korea have soared since a 2011 free-trade deal eliminated duties on vehicles imported from Europe. Vehicle imports from Germany rose 18.2 percent to $4.5 billion in the first eight months of 2015, South Korean customs data show, following a 42.5 percent increase for all of 2014.
Volkswagen and Audi accounted for 28.2 percent of all foreign cars sold the in the first eight months, according to the Korea Automobile Importers and Distributors Association.
Suh Sung-moon, analyst at Korea Investment & Securities, said local brands such as Hyundai and its sister firm Kia Motors would benefit.
"South Korean consumers are very sensitive to news, and this emission news will have an impact on the import market," he said.