A South Korean woman tested positive for swine flu in additional examinations after traveling to Mexico, making her a "probable" case - the country's first - authorities said Tuesday.
Final tests are still necessary to confirm whether the woman, 51, has swine flu, the Korea Centers for Disease Control and Prevention said in a statement.
The woman has remained quarantined since returning from a trip to Mexico on Sunday. She contacted authorities upon her return, complaining of high fever, cough and a runny nose, officials said.
All 315 others on the same flight from Los Angeles were being tested but none have turned up positive, officials said.
Two others with possible swine flu symptoms tested negative for swine flu, which has killed more than 150 people in Mexico.