Twenty-one people have been injured, two seriously, as a train derailed in a crash with a lorry on a level crossing in Suffolk.
The two-carriage diesel passenger train was in collision with the sewage tanker in Little Cornard, Sudbury, at about 1735 BST.
Network Rail said the train driver of the 1731 service from Sudbury to Marks Tey was one of two seriously hurt.
A 38-year-old man has been arrested on suspicion of railway safety offences.
Suffolk Police have described the crash, at the level crossing in Sewage Works Lane, as a "major incident". Fire crews are also at the scene.
The lorry was split open in the collision, spilling slurry over the scene.
The East of England Ambulance Service said two people who had been trapped on the train suffered life-threatening injuries.
Two others also suffered injuries which were less serious. It described the others as "walking wounded".
British Transport Police (BTP) later said one person remained in intensive care.
The train driver suffered suspected fractured vertebrae and was being treated at Colchester General Hospital.
At least one person was airlifted to Addenbrookes Hospital in Cambridge.
Superintendent Phil Trendall of BTP said: "Clearly if the train had turned over the injuries could have been greater. We are just grateful the injuries were no greater in seriousness or in number."
BTP said there were 20 people on board the train.
One of those was Lee Bloomfield, 17, who was on his way home from work, and suffered chest injuries.
"I felt a sudden collision as the train didn't slow down. I shot forward and hit the table and I banged my chest," he said.
"When I got up, I saw the cab of the tanker on one side of the track."
A fire service spokeswoman said it had been the rear of the train's two carriages which derailed in the crash. Both train carriages remained upright.
Network Rail said the level crossing was on private land and had a locked gate on it.
A spokesperson said anyone wanting to go across the level crossing needed to call the signaller to raise the gates.
However, the spokesperson said Network Rail had not received any calls prior to the crash.
Sharon Smith, 49, who was in her nearby garden when the crash happened, said: "I heard a massive bang.
"Everybody in the area ran to see what happened.
"At first I thought it was a car accident. But when I ran up the road I could see two carriages had hit a tanker."
She said many passengers got out of the train and gathered at the sides of the road.
Ms Smith said she stood in the road to help clear traffic.
Network Rail said the train involved was a service run by National Express East Anglia.
In a statement, it said: "The crossing is a user-worked crossing with gates and telephone.
"The Network Rail signaller did not receive a phone call from the user of the crossing."
Train services were being replaced by a bus service on the Sudbury to Marks Tey route, with the line unlikely to reopen before Friday, Network Rail said.