Despite all of them testing negative for Covid-19 before departure, seven of the 132 people who were repatriated from India to Malaysia earlier this week were later found positive with the virus.
All 132 have since been placed under a 21-day quarantine for monitoring.
When contacted, Health Ministry director-general Dr Noor Hisham Abdullah said the longer quarantine period will enable the ministry to study how the seven cases evaded initial detection.
“Well, this new variant, we do not know exactly the behaviour of the virus.
“What we do know is it spreads rapidly with a high fatality and may be evasive to testing initially. Hence, we need a longer period of quarantine,” he said.
Only Covid-19 negative passengers were allowed on the May 12 flight.
Onboard the specially chartered Malindo Air flight were 117 Malaysians, six dependents, one Malaysian permanent resident, and eight Brunei nationals.
Noor Hisham said the ministry has yet to determine if the seven positive cases were variants of concern.
“The sample for a full genomic sequence has been taken and it takes time, as we need to culture the virus before full genome sequencing,” he said.
India is among the countries worst-affected by Covid-19.
The B.1.617 Covid-19 variant of global concern originates from the South Asian nation and is reportedly more infectious, including being able to cause serious illness in those below 50 years old.
Malaysia previously recorded two cases of the Indian variant.
The first case was an Indian national who arrived from India last month and tested negative for Covid-19 twice. However, he later suffered severe Covid-19 symptoms and died on April 21.
The second case was also a traveler who arrived in Malaysia on April 10 and subsequently tested positive.
Passenger flights from India have been banned except for Malaysians and their dependents returning on humanitarian and disaster relief flights.
All arriving from India will now need to quarantine for 21 days.