A Melbourne man had travelled to some of the city’s busiest train stations while infectious with COVID-19, the Victorian Health Department has revealed.

Commuters who hopped on the Craigieburn to Southern Cross service at 5.28pm on Friday, and Flinders Street to Craigieburn service at 10.20pm that same day have been urged to get tested and isolate until a negative result is returned.

The two new Metro train lines were added to a growing list of COVID-19 exposure sites late on Tuesday, as authorities say evidence of community spread could trigger boosted restrictions.

Ten other COVID exposure sites were announced after a man in his 30s tested positive at his home north of Melbourne.

He flew into Adelaide from India via the Maldives and Singapore on April 19 before Australia’s flight ban began.

After completing quarantine at the Playford Hotel, he returned to his home in suburban Melbourne’s Wollert early last week and developed symptoms on Saturday before testing positive on Tuesday.

South Australian authorities are examining whether the man contracted the virus before arrival and had an unusually-long incubation period, or caught it from a person with the virus in a neighbouring hotel room.

Victoria’s Chief Health Officer Brett Sutton suspects the man picked it up in the hotel, not India or on his international flights.

All three of the man’s household contacts have returned negative test results, with Prof Sutton describing it as an “early encouraging sign”.

South Australia’s genomic sequencing report could shed light on the source of the man’s infection but is expected to take 48 hours to complete.

Authorities are naming more ‘exposure sites’

As of Wednesday morning, there were four “Tier 1”, five “Tier 2”, and three ‘Tier 3’ exposure sites.

The “Tier 1” exposure sites include an Altona North office where the man worked, an Indian restaurant in Melbourne’s CBD and a supermarket in Epping.

• The full list of exposure sites is available here.

Anyone who visited the sites at specific times must get tested and isolate for 14 days from exposure.

Tweet from @VicGovDH

Victoria’s COVID-19 response boss Jeroen Weimar said evidence of community spread within Melbourne would prompt officials to consider “the next set of appropriate measures”.

“I’m not going to sit here and speculate on what that might be,” he told ABC Melbourne radio on Tuesday.

“If we are finding positive cases in the workplace or exposure sites that would obviously be a significant cause for concern.”

He said it appeared not all of the 30 to 40 diners in the ‘Tier 1’ Curry Vault restaurant on Friday night checked in with the Services Victoria QR code system.