Trains on the Seymour line have been suspended due to an emergency services incident in Pascoe Vale.
Between Southern Cross and Craigieburn, Seymour V/Line trains are not operating.
Passengers will instead switch to a Metro Train service and rail replacement buses for connections between Craigieburn and metropolitan stations.
The incident resulted in the closure of Gaffney St in Pascoe Vale, and the suspension of trains on the Craigieburn Line between Broadmeadows and Essendon stations.
Trains are continuing to operate between Essendon and Flinders Street stations, with delays expected.
The Department of Transport and Planning recommends passengers travelling during the morning peak period to check station platform displays, listen for announcements and allow up to 35 minutes extra for their journey.
Real-time traffic conditions can be found at transport.vic.gov.au