The 50-year-old porter was on Sunday confirmed to be infected with the Delta variant of the coronavirus.
The centre said a genetic analysis showed this case was unrelated to an airline ground crew member who was infected more than two weeks ago.
Instead, it found that the porter worked on a cargo flight which arrived from Moscow on July 6. One of the crew members on the flight was also confirmed to have Covid-19.
The centre said the genomes of the viruses contracted by the porter and the aircrew member were found to be related.
It said although the porter had no direct contact with the aircrew member, he had worked in the cabin of the plane for several hours, in the presence of other aircrew members.
It said the porter might have been infected from some undiagnosed crew on the flight.
Meanwhile, the centre reported one new Covid-19 case on Tuesday, involving a 27-year-old woman who flew in from Cambodia.
She tested positive for the virus while undergoing quarantine at a hotel in Shek Tong Tsui.