Hong Kong has stopped inoculations using the BioNTech COVID-19 vaccine pending an investigation into possibly defective packaging.

Fosun Pharma, which is distributing the product in China, reportedly told Hong Kong officials that a batch of the Pfizer/BioNTech vaccine had defective bottle lids. The suspicious batch included 585,000 doses.

Fosun Pharma and BioNTech are investigating the matter, but said they believe any doses affected by the defective bottle lids are still safe. The investigation means that Hong Kong residents may only receive the authorized Sinovac vaccine at present.