Network Rail said it had been forced to close the line between Doncaster, Goole and Scunthorpe after the track became unsafe, and today engineers were still working on a solution.
A train driver first reported concerns about the uneven track near Hatfield Colliery, Doncaster, on Saturday, but it was not closed until yesterday morning when pit staff raised the alarm.
The working colliery, one of the last remaining in the country, is managed by Durham-based mining company Hargreaves.
A spokesman for the firm said it had called in specialist civil engineers to tackle the problem but could not predict how long the work would take.
He added: “We have brought in a team of external civil engineering experts and as we speak they are conducting a thorough investigation and assessment.
“They are trying to work out the possible cause and best solution.”
Network Rail said a number of services were affected, with buses replacing trains between Doncaster and Goole and Doncaster and Scunthorpe, with journey times being extended by up to an hour.
Other service alterations yesterday included the diversion of services between Sheffield, Hull, Scarborough and Bridlington via Selby, and the suspension of the First TransPennine Express service from Manchester Airport and Cleethorpes between Doncaster and Scunthorpe.
A Network Rail spokesman said: “We anticipate that there will be disruption for some time.
“Our engineers are working with the colliery to understand the cause of the movement of the spoil heap and to develop a safe plan to manage this and restore the track.”