Rush hour rail journeys were cancelled this morning after a body was discovered close to the tracks.
Emergency services attended the scene, close to Lostock Station near Bolton, before the day's first service was due to depart.
The cancellations affected dozens of services between Preston, Bolton and Wigan including Chorley and Buckshaw Parkway. Commuters and holidaymakers travelling to Manchester Piccadilly and Manchester Airport were also affected after connecting services at Preston were cancelled.
At around 9.45am, trains were running again between Bolton, Preston and Wigan in one direction but no services were able to travel through Lostock station towards Bolton.
Northern said that disruption is expected to last until around noon but replacement buses are operating.
A statement from Northern said: "All services are suspended between Bolton-Preston and Bolton-Wigan due to an ongoing incident involving the emergency services.
"Disruption to services is likely until midday. Rail replacement buses have been arranged to operate between Bolton and Preston/Wigan whilst emergency services are on-scene.
"We apologise for any delay this may cause to your journey."