Customs officers on Sunday warned people considering buying Covid-19 drugs that aren't registered with the authorities that they're in danger of spending cash on medication that may not work and could even be unsafe.

The comments follow the seizure of about 380 boxes of suspected contraband Covid medication in the past four days.

"We found no Hong Kong registration number in this batch of Covid oral drugs, so we believe these are unregistered pharmaceutical products," said Inspector Hong Yan from the Syndicate Crimes Investigation Bureau. "Therefore, the related drugs' efficacy, safety, and quality are questionable."

"Members of the public should not buy pharmaceutical products from unknown sources," Hong said.

He also called on buyers to check the five-digit HK registration number on the packaging of pharmaceutical products.

The suspect drugs, with a total estimated market value of about HK$500,000, were seized at Hong Kong International Airport and in a Tin Shui Wai flat.

A 34-year-old woman and a 40-year-old man have been arrested in connection with the case and released on bail. They're suspected of importing pharmaceutical products without a licence and of possessing poisons.