Hong Kong is using a raft of detective methods to find six diners who may have been exposed to COVID-19 in its first cluster of local omicron infections, since the city’s location-logging app doesn’t disclose their contact details.

Officials have identified 201 out of 207 patrons of the Moon Palace restaurant where an aircrew member from Cathay Pacific Airways Ltd., who was subsequently found to be infected with omicron, was eating lunch with his family on Dec. 27. Five other customers later tested positive, and 191 so far have been sent to a government-run quarantine center where they will be regularly tested for the pathogen.

But six diners across two tables have yet to be identified. It’s an unacceptable risk for Hong Kong, where the government has imposed increasingly strict regulations as part of its zero tolerance approach to controlling COVID-19.