Epidemiologist Benjamin Cowling said on Wednesday he was sceptical that a 17-year-old girl had contracted a mutant Covid strain from contaminated food packaging.
On Tuesday, health authorities said a sample of frozen crocodile spare ribs from Thailand in the girl's freezer had tested positive.
The girl became infected earlier this month, breaking Hong Kong's more than 40 days without an untraceable case.
Professor Cowling from the University of Hong Kong's School of Public Health said packaging wasn't a major route of transmission.
"It is unlikely at this point that the infection did occur from contaminated meat packaging," said Cowling. "For this particular possibility, I think the next step is really to look at whether the virus matches."
"Can we say it's the same virus on the meat packaging as the virus that infected the girl? Was it the virus on the meat packaging first, and then infecting the girl, or was it that the girl had the infection and breathed on the packaging of meat and that's how the virus got there – and because it was frozen it was able to stay there?"
The girl has reportedly admitted to sneezing on the package, suggesting the package was not the source of the virus.
Late on Tuesday the government's Centre for Food Safety announced that it had ordered the vendor to stop selling the frozen crocodile ribs, and to provide product samples for testing.
The government said at the end of May that over 10,000 samples of food and their packaging had been collected for testing. The results, including those for over 40 related crocodile products imported from Thailand, were all negative.