Northern reported that, due to a tree on the line at Darton, all lines between Barnsley and Wakefield Kirkgate stations were blocked in both directions.
All services are prevented from passing through the area.
Northern first reported the delays shortly before 10am, and said that delays should be expected until 12pm today (Friday).
In a statement, Northern said: “Due to a tree blocking the line between Barnsley and Wakefield Kirkgate all lines are blocked.
“Train services running through these stations may be cancelled, delayed or revised.
“Staff are due on site soon to assess the size of the damage and to provide an assessment of how long it will take to cut the tree and remove it from the railway.”
Services between Wakefield Kirkgate and Leeds are running as normal.
Rail replacement services have been recruited and will depart from Wakefield Kirkgate to Barnsley at 10am, 11am, 11.30am and 12pm.
Replacement services from Barnsley to Wakefield Kirkgate will depart at 10am, 10.30am and 11am.
It is expected that journey times will be extended by up to 45 minutes.