Four new COVID-19 cases have been uncovered among a family in Melbourne’s north, sparking a search for the source of the outbreak. Health Minister Martin Foley confirmed two more people had returned positive coronavirus test results, on top of the two cases revealed earlier on Monday. Health authorities were alerted to the unfolding cluster when a Whittlesea man presented for testing on Sunday after developing symptoms on Thursday. He and another man, a male relative from a separate household, both tested positive. A woman and pre-school-age child living with the Whittlesea man have also since been confirmed as COVID positive. Other family members among the two households are also in isolation and have so far tested negative. Highpoint Shopping Centre in Maribyrnong and a Bundoora swimming school have been listed as initial exposure sites. Anyone who attended the “tier one” sites at specific times on Thursday and Friday must get …