Seoul - South Korean health authorities Friday reported two additional suspected cases of infections with the new variant of influenza A(H1N1), commonly known as swine flu. The report by the Korea Centers for Disease Control and Prevention (KCDC) caused concern that a human-to-human transmission of the highly contagious disease took place in the country, the national Yonhap news agency said.

According to KCDC, a female patient in her 40s is being tested for having contracted the influenza A virus without travelling to affected countries.

She lived with another woman who was reported Tuesday as the first probable case of swine flu in South Korea.

The first patient, a 51-year-old woman, who returned from a trip to Mexico last weekend, has been quarantined at a hospital and is reportedly recovering.

As of early Friday, 18 Koreans are still being tested for the virus as suspected cases and three people are categorized as probable cases, said the KCDC in its latest report.

South Korea has restricted travels to Mexico, the epicentre of the outbreak, while tightening quarantines of pork imported from affected countries.