Victoria's myki card readers offline during peak hour

"We are working to restore it as soon as possible," a department spokesman told AAP.

"We thank passengers for their patience until this issue is resolved."

The outage was affecting most myki fare payment devices at the state's train stations, buses and trams. 

AAP understands technicians are working to resolve the issue although the outage could continue for some hours. 

It comes after heavy rain lashed the Melbourne CBD on Thursday evening, leaving hundreds of homes without power.