Train chaos is easing after Metro removed the balloons that were caught in overhead wires between Flinders Street and Southern Cross stations, temporarily stalling four railway lines.
Trains are running through the City Loop on all lines now, except for the Upfield line which is still suspended.
There are 15 minute delays on the Cranbourne, Pakenham and Frankston lines, both into and out of the city.
Stray balloons cause train delays
Metro staff remove balloons stuck in overhead wires between Flinders Street and Southern Cross stations.
Metro spokesman Daniel Hoare said the multiple track and signalling faults were not caused by today's high temperatures.
Buses have replaced trains between North Melbourne and Upfield. Commuters have been asked to defer travel if they can.