A cleaner stole an empty commuter train from a depot and drove it off the rails and into a Swedish apartment building.
Police said the woman was seriously injured in the early morning crash outside Stockholm and was flown to hospital. No one else was hurt.
Train operator Arriva said the woman, in her 20s, stole the four-car train at a depot outside the city.
She then drove it about a mile to the end station on the railway line, where it jumped off the tracks and crashed into a three-storey building.
"There were three families inside the apartment building, but no one was injured. At least not physically," an Aviva spokesman said.
It was not known whe the woman, who worked for a company contracted to carry out cleaning for the train operator, took the train.
"We have only heard good things about her. We're investigating how this could happen, and why she did what she did," said the spokesman.
He did not know how she got the keys to the train, but added that driving it was not complicated.
"Generally speaking that's possible even if you're not a train driver," he said. "You can read about it on the internet, or observe how others do it."