But a PCR nasal swab test later confirmed the workers had returned "truly negative" results. "Out of an abundance of caution, intermediary measures were taken place around each of those places of work ... until those PCR tests were then followed up," Health Minister Martin Foley said. Health authorities are continuing to manage, monitor and test the remaining primary close contacts apart of the cluster, Mr Foley said. A total of 546 people associated with the Melbourne Airport exposure site at Terminal 4 have been released from isolation after being "reclassified". "We thank those people for isolating and their support," Mr Foley said.