Craigieburn line services have been suspended until further notice after a truck became wedged underneath the Racecourse Road bridge in Flemington about noon on Friday.
The trains were suspended due to loss of signal power caused by the accident, Metro reported on their website. Maintenance crews are fixing the problem but Metro have not specified when trains might resume.
Buses are on order while a tow truck is attempting to remove the truck.
Traffic in the area has been disrupted.
The buses will replace trains between North Melbourne and Essendon, said Metro.
Motorists are reporting traffic gridlock in the area due to the accident.