The travelers arrived at the airport via two separate flights. All of them tried to enter the US through the Electronic System for Travel Authorization, a travel document under the South Korea-US visa waiver program.

ESTA permits citizens of South Korea to travel to the US for tourism or business for up to 90 days without a visa, but US authorities found that they tried to enter the country for other purposes, according to the foreign ministry. The ministry, however, refused to give the details of their visiting purposes, citing privacy reasons.

"The South Korean Consulate General in Atlanta contacted the US Customs and Border Protection to find out why our citizens were denied entry and were ordered to leave," an official with the foreign ministry said. "We've checked whether the travelers received translation services and other amenities in the process."

To prevent such cases from happening again, the foreign ministry said it will soon contact CBP officials and promote related information to the public when they plan for US travel. (Yonhap)