Melbourne is on the edge of its fourth lockdown with health authorities and state cabinet in crisis meetings on Wednesday night as they raced to contain the ballooning COVID-19 outbreak which has risen to 15 cases and more than 60 exposure sites.

Acting Victorian Premier James Merlino said earlier on Wednesday the next 24 hours were “critical”, with exposure sites now extending beyond Melbourne’s northern suburbs to the wider city and regional Victoria, including the MCG, Marvel Stadium, bars, cafes, shopping centres and a car finance workplace in Port Melbourne.