No trains are currently running between Victoria Station and Rochdale due to a points failure.
The line is blocked while engineers work to fix the issue, Network Rail said.
It will affect services between Manchester Victoria and Leeds and between Clitheroe and Rochdale.
Disruption is expected until 11am.
A post on the Network Rail website says: "A points failure between Manchester Victoria and Rochdale means all lines are blocked.
Train services running through these stations will be cancelled, delayed by up to 30 minutes or revised.
"All stations between Manchester Victoria and Rochdale will not be served.
"Disruption is expected until 11am."
Northern ticket holders will be able to travel on the Metrolink between Manchester Victoria and Rochdale, and also on TransPennine Express services between Manchester Victoria and Leeds via Huddersfield.
