An inferno has killed 20 people and injured 12 others, most of them elderly, aboard a coach on a motorway near Hanover in northern Germany.
Police believe the fire started in the toilet and engulfed the coach in seconds. A burning cigarette is thought to have caused it.
Some of the victims had difficulty walking and were unable to escape in time, the tour company said.
The victims, from the Hanover area, had been on a day trip.
At least four of the injured have serious burns and there are fears the death toll may rise in what officials say is the worst coach disaster for 16 years in Germany.
Fierce blaze
The fire on the bus started at about 2040 local time (1940 GMT) on Tuesday, police said.
Flames must have shot out of the toilet "at lightning speed", a Hanover traffic manager, Uwe Hollstein, said.
"Someone was smoking secretly in the toilet and that's what started the fire. It happens," said Oliver Pehl, whose mother owns the coach company.
The driver - who was also among the injured - managed to pull over to the hard shoulder on the A2 Autobahn but the blaze was too fierce to extinguish.
The burnt-out coach has now been taken to Hanover and investigators are trying to identify the bodies.
Mr Pehl said he had driven the coach himself in the past and it had never had any problems.
"It is terrible, just terrible that so many people lost their lives," he said.
Police say a technical defect was not to blame.
'Deeply shaken'
A police spokesman, speaking anonymously, said the bus had caught fire while driving along and that no other vehicle had been involved.
"The passengers did not manage to get out of the burning vehicle in time," he said.
"I just saw smoke and then I got closer and closer and realised that a coach was on fire," eyewitness Nadia Possberg told Reuters.
Another eyewitness said what he saw was "just horrible".
German Transport Minister Wolfgang Tiefensee said he was "deeply shaken by the dreadful fate of the victims of the fire" and sent his condolences to their families, reported AFP.
Mr Tiefensee said there would have to be an investigation into the cause of the fire and whether safety regulations had been followed.
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