"The CIB are investigating a sudden death incident to determine what happened," said Hall.
It's understood the death is not being treated as suspicious.
Auckland Transport spokesman Mark Hannan said commuters weren't affected as buses had replaced trains while maintenance work was being carried out on that line today.
Hannan said a freight train was involved in the incident.
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (4pm to 6pm weekdays)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• The Word
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.