Engineers are trying to repair damaged tracks after a train collided with a sewage tanker on an unmanned rail crossing.
Twenty-one people were injured, one of them seriously, in the crash at Little Cornard near Sudbury, Suffolk, on Tuesday.
The front carriage of the two-car National Express East Anglia service, which was carrying more than 20 passengers, derailed in the incident.
Witnesses spoke of hearing a sound like a bomb explosion when the train and truck collided at 5.35pm, and then seeing dazed, bleeding passengers wandering around next to the track.
The lorry was also split open by the crash impact and spilt slurry on the crossing – creating a health hazard and making repairs to the track more difficult.
Train services were being replaced by a bus service on the Sudbury to Marks Tey route, and Network Rail said the line is unlikely to reopen before Friday.
While train safety generally has improved in recent years, level crossing accidents are still a cause of concern to the rail industry and itsregulators.
Last year there were as many as 3,244 recorded incidents of misuse or error at level crossings, following 3,495 incidents in 2008.
Investigators are focusing on the actions of the tanker driver and whether he made contact with the signal box.