An investigation was continuing on June 23 into how a man came to be found dead on rail tracks between Kennington and Radley.
Passengers on the 10.48pm Thames Train from Paddington were concerned when the train jolted to a stop at about 11.50pm on June 20, near Kennington Junction.
It remains unclear exactly how the incident occurred.
A transport police spokesman said: "It's a non-suspicious incident at the moment, but we're still investigating."
The line was closed for an hour and other trains between Oxford and Didcot were cancelled, with passengers being put into taxis.
Academic consultant, Michael Carmichael, 57, from north Oxford, was on the train from Paddington when it came to a sudden halt.
He said: "It was a very rapid stop and we could smell the brakes.
"We were there for about an hour and 45 minutes and saw police looking under the train, then saw an ambulance pull up.
"A young passenger then came on and said that he had heard that someone had been seen running, then went in front of the train.
"We don't know if it was a suicide or a terrible accident but the driver had no chance of stopping."
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