Emergency services are dealing with an incident between Bournemouth and Brockenhurst and all lines are currently blocked.
A number of trains services are currently trapped within the blockage.
Remaining services are subject to changed whilst emergency service deal with the incident.
Special bus services from Southampton are being arranged and will replace services.
It follows an incident involving a person jumping in front of a train.
The line is likely to remain blocked for the rest of the evening.
A spokesman for the British Transport Police said: “At 8.44pm officers were called to Pokesdown station after reports of a casualty on the tracks. Paramedics also attended. A 16-year-old girl from Christchurch was sadly pronounced dead at the scene, her family have been informed.