HEALTH authorities are racing to track down hundreds of fans who went to last Friday's AFL match on the same train as a man with COVID-19.

There are fears crowds of people 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's Health Minister Martin Foley said a large number of people may have been exposed on the train or at the station.

"It's in the many hundreds, particularly the later train back, because it was after the AFL game," he told the media on Wednesday.

The AFL has sent text messages alerting all of the 54,857 people who attended

The Craigieburn to Southern Cross service between 5.28pm and 6.07pm on Friday has been listed as a tier two exposure site, along with the Flinders St to Craigieburn service between 10.20pm and 11.05pm.

Craigieburn and Southern Cross stations last Friday night have also been listed as tier three exposure sites.

Authorities are also working with Metro Trains to contact passengers, and have urged anyone who was on the train to isolate and get tested.