The body was found on a line at Chester-le-Street between Newcastle and Durham.
The incident left all lines blocked but London North Eastern Railway says that the lines have re-opened.
National Rail said earlier that some trains were being diverted via Sunderland.
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LNER tweeted: #LNERUpdate The line has now reopened.
"Customers who have been delayed 30 minutes or more will be able to claim our Delay Repay scheme."