Hundreds of passengers were stranded on trains, some for more than four hours, after a body was discovered on a railway line.
Services were suspended on the East Coast Main Line at around 9pm yesterday after a man's body was found in Stoke Tunnel, near Grantham, Lincolnshire, a spokesman for train company East Coast said.
British Transport Police (BTP) declared the line open again at 1.49am.
Seven northbound and six southbound East Coast trains, containing 1,800 people, were affected.
One train was suspended in a tunnel and another was in an open area, while the rest were sitting at stations, the East Coast spokesman said.
He added: "We have been very concerned for the welfare of our passengers and tried very hard to keep them comfortable with food and water on board.
"It's frustrating for our customers. In this situation we are entirely in the hands of BTP.
"It all depends on how long it takes the emergency services to clear the site and declare it open again."
It was not clear how many passengers chose to get off the stationary trains.
Other train companies which use the line may also have been affected, he added.
BTP officers and Lincolnshire Police attended the scene, near Great Ponton, after receiving reports of a body on the line at about 9.15pm.
A BTP spokesman said in a statement: "Inquiries are continuing to establish the identity of the man and the circumstances leading up to his death.
"The incident is currently being treated as unexplained. A file will be prepared for the coroner.
"The train involved has yet to be established and inquiries are ongoing."
Explaining the length of time it took to reopen the line, Inspector Chris Fellows of BTP said: "Because the death is unexplained it is treated in a different way from a non-suspicious death.
"As we don't have an immediate explanation certain things have to be done, such as a forensic examination of the site, before we can remove the body and reopen the line."
Anyone with information is asked to call BTP on 0800 405040.