SINGAPORE - Initial investigations have shown that a traveller who tested positive for Covid-19 in South Korea after transiting in Changi Airport was unlikely to have been infected in Singapore, said the authorities on Friday (July 31).

"The source of infection remains unknown and investigations by the various authorities are ongoing," said the Ministry of Health (MOH) and Civil Aviation Authority of Singapore (CAAS) in a joint statement on Friday. "As an added precaution, contact tracing in Singapore is also underway."

The person left New Zealand on July 21 and arrived in South Korea on July 22, when a polymerase chain reaction test done four hours after the person's arrival was positive for the virus.

South Korean authorities subsequently informed New Zealand that they suspected the person, who showed no symptoms, had been infected during the transit in Changi Airport.

But this would have meant an incubation period of less than 24 hours, Singapore authorities said.

According to the World Health Organisation, the average incubation period for Covid-19 is five to six days, up to a maximum of 14 days.

"Singapore is in contact with the New Zealand and South Korea authorities for further information," said MOH and CAAS.

The authorities added that stringent measures are in place to ensure that passengers transiting through Changi Airport are segregated from all other passengers at all stages of their journey.

Airport staff wear personal protective equipment when interacting with passengers, while passengers are required to wear masks at all times.

"Safe distancing, temperature taking for passengers and staff are also enforced," they said. "All transit passengers, including those who had arrived on the same flight as the individual, adhered to these precautionary measures."