A group of travellers who were quarantined on the same floor of an Adelaide hotel as two positive COVID–19 cases have been sent back into isolation.

A man in his 30s tested positive for coronavirus while at home in Wollert, located 26 kilometres north of Melbourne’s CBD,  just days after leaving quarantine at the Playford hotel in South Australia.

Genomic testing later confirmed the man had contracted COVID-19 while in hotel quarantine, where he stayed next door to a person who had tested positive to the virus.

Health authorities have since sent 34 fellow guests back into quarantine for a further two weeks.

The group includes ten South Australian guests who will be given the option to quarantine at home if deemed suitable.

Three people will need to return to medi-hotel quarantine as their homes were deemed unsuitable.

South Australian Chief Health Officer Nicola Spurrier stressed most medi-hotel staff working at the time of the suspected leak had undergone daily testing, although five are still awaiting test results.

Ms Spurrier also confirmed the two cases had been genomically linked late on Wednesday.

“Investigations into the precise cause of transmission are ongoing,” Ms Spurrier said.

She clarified on Thursday that there is no further risk of transmission in that hotel.

Local health authorities on Wednesday barred travellers from entering the state if they had visited any of Victoria’s high-risk exposure sites, with few exceptions.

The move came as Victorian health colleagues scrambled to track down hundreds of fans who went to last Friday’s AFL match on the same train as the infected man.

The AFL sent text message alerts to all 54,857 spectators, amid fears hordes may have been exposed to the virus on the Craigieburn line train while travelling to or from the Geelong-Richmond match at the MCG.

Victoria has not recorded any new local COVID-19 cases since Tuesday, with the Wollert man to remain in isolation for two weeks.

More than 21,900 tests were received as confidence grows that the state’s coronavirus scare has been contained.

Tweet from @VicGovDH

Meanwhile, health authorities say more than 40 tests from Tier 1 exposure sites have come back negative for coronavirus.

Twelve exposure sites have been identified in Melbourne – including a CBD restaurant, grocery shops and convenience stores in Epping, and two train services that are believed to have taken people from the football at the MCG on Friday night.

The state government said it will step up compliance checks on businesses after it emerged that several patrons who attended a CBD restaurant alongside the infectious man on Friday night did not use the QR check-in system.

Health Minister Martin Foley warned people will soon face tough penalties if they fail to check in with QR codes at venues.

• Related: QR code complacency will lead to lockdowns

There have been no locally acquired cases of coronavirus in Victoria for 76 days.

Victorian COVID-19 exposure sites

Tier 1: Get tested and quarantine for a full 14 days
Pact Retail Accessories (until recently called TIC) front office, Altona North, 8:15am-5:15pm May 6
Woolworths Epping, 5:40pm-6:38pm May 8
Indiagate Spices and Groceries, Epping, 5:00pm-6:00pm May 8
Curry Vault Indian restaurant and bar, Melbourne CBD, 6:30pm-9:30pm May 7

Tier 2: Get a test and isolate until you receive a negative result
Pact Retail Accessories (until recently called TIC) back warehouse, Altona North, 8:15am-5:15pm May 6
7-Eleven Epping, 6:30pm-7:00pm on May 6 and 11:10am-11:40am May 8
Train service which left Craigieburn 5:28pm and arrived at Southern Cross 6:07pm May 7
Train service which left Flinders Street 10:20pm and arrived at Craigieburn 11:05pm

Tier 3: Monitor carefully for symptoms and get tested and isolate if they emerge
Craigieburn Railway Station 5:23pm-5:28pm on May 7
Southern Cross Station 6:07pm-6:22pm on May 7
Flinders Street Station 9:50pm-10:50pm May 7
Current as of 12:00pm Wednesday, May 12.

-with agencies