Hong Kong's government said an initial investigation by Germany's BioNTech and Fosun Industrial into its coronavirus vaccine did not show any "obvious systemic factors" during packaging after use of the vaccine was suspended in the city and neighbouring Macau this week.
Authorities on Wednesday halted the use of a Covid-19 vaccine developed by BioNTech citing defective packaging, triggering confusion in inoculation centres across the city.
The suspension came as the Asian financial hub has faced a sluggish take-up of vaccines due to dwindling confidence in China's Sinovac vaccine and fears of adverse reactions.
In a statement published late on Saturday, the city's government said the investigation results did not rule out that the situation was "caused by environmental conditions during the long-haul transport process."
It was not related to the cold-chain and logistical management of the vaccine and random testing of intact vials delivered to Hong Kong did not uncover any issue of leakage, it said.
Both Fosun and BioNTech considered the vaccines to have no safety risks and people who have received them "do not need to worry", the government said.
The remaining part of the investigation will focus on "ascertaining the integrity of the intrinsic properties of the relevant batches of vaccine, and that the batches are safe for use."
The government said it was following up with Fosun and BioNTech to complete the investigation within a week to allow for a resumption of supplying the vaccines to the public.
The city started vaccinating residents with doses from Sinovac in February and began offering the one developed by BioNTech in March.
The BioNTech vaccine is distributed in Hong Kong and Macau via a partnership with China's Fosun Pharma, while BioNTech partners with Pfizer in markets outside greater China.