The disruption has affected trains running between Weymouth and London Waterloo.
It comes as an incident took place near the railway between Andover and Basingstoke with all lines between Salisbury and Basingstoke closed whilst emergency services were on the scene.
A spokesperson for South Western Railway (SWR) said: “Due to the emergency services dealing with an incident near the railway between Andover and Basingstoke, all lines are blocked.
“Train services running through these stations may be cancelled, delayed or revised.”
In the latest update, SWR said: “We can confirm that all lines reopened at 4.45pm. Trains are starting to return to normal, but customers should expect delays and cancellations until around 8pm.”
It is not yet known what the nature of the incident was. British Transport Police have been contacted for more information.