Hong Kong suspended vaccinations using Pfizer shots known as BioNTech shots in the city on Wednesday after they were informed by its distributor Fosun that one batch had defective bottle lids.

The suspension was immediate while Chinese pharmaceutical firm Fosun Pharma and BioNTech, the German company which created the vaccine with American pharmaceutical firm Pfizer, investigate the matter, according to a statement by the Hong Kong government.

BioNTech and Fosun Pharma have not found any reason to believe the product is unsafe, according to the statement. However, vaccinations will be halted as a preventive and safety measure.

The defective lids were found on vaccines from batch number 210202. A separate batch of vaccines, 210104, will also be not be administered. Macao also said Wednesday that residents would not receive the Pfizer vaccinations from the affected batch.

All community centers in Hong Kong administering the Pfizer vaccine have temporarily suspended vaccinations and residents who already made appointments for Wednesday need not proceed to the centers, the government said.

The suspension of the Pfizer jab means the only vaccine currently offered to residents is China’s Sinovac vaccine. The two vaccines are the only ones that were offered to residents in Hong Kong.