LONDON: A train derailed after colliding with a sewage tanker at a railway crossing in Britain, injuring 21 people, one of them critically, emergency services said.

The front carriage of the two-car train came off the tracks late Tuesday after smashing into the lorry in the village of Little Cornard, southeast England. The carriage did not tip over but remained upright.

Witnesses said they heard a sound like a bomb exploding when the train and truck collided at 5:35 pm (1635 GMT) and then saw dazed passengers covered in blood wandering around near the scene of the accident.

The lorry burst open on impact, spilling sewage across the tracks.

The driver of the lorry was arrested on suspicion of several railway safety offences. Drivers wanting to use the unmanned crossing have to phone railway authorities from the site to obtain permission.

One person trapped on the train sustained life-threatening injuries and was in intensive care, said British Transport Police.

Twenty other people were hurt but their injuries were not life-threatening.

"There was a very, very loud bang. I`ve never heard anything like it. I thought it was an aeroplane crash or a bomb going off," said Jack Barnett, 65, a retired lorry driver who lives close to the scene of the crash.

BDST: 9:29 HRS, August 18, 2010