A tour bus returning from a day trip to a farm caught fire on a highway near the northern German city of Hannover on Tuesday night, killing 20 people, after a passenger reportedly sneaked a cigarette, police said.
Survivors told authorities the fire broke out in the bathroom of the bus as it drove down the A2 highway after a person apparently smoked a cigarette there, police spokesman Stefan Wittke said.
When the door was opened, flames shot out and quickly engulfed the bus, he said.
"Passengers who were sitting close to the exit could get away, but the others had no chance," said fire department official Claus Roehrbein.
Thirteen people were injured in the blaze, including three with serious burns, according to the fire department.
The bus had 39 primarily elderly passengers and the driver aboard, according to the Hannover-based company Mommeyer that owns it. Wittke, however, said 33 people were aboard the bus. It was not possible to immediately reconcile the difference.
The bus had been chartered by a tour group to go from Hannover on a day trip to a farm, Uwe Prehn, the husband of the bus company owner, told The Associated Press by telephone.
It was on its way back to Hannover when the fire broke out. Wittke said all the passengers were local people but did not have their nationalities available.
Bild newspaper posted a picture of the scorched wreckage of the bus, its back window blown out, at the side of the road with firefighters nearby.
The bus apparently pulled off into an emergency lane before it was engulfed in flames, but many people were unable to get off in time, Bild reported on its Web site.
Transport Minister Wolfgang Tiefensee said he was "deeply shocked" by the accident and called for a careful investigation into the cause of the fire, and into whether safety regulations were followed.