STOCKHOLM (AP) — A double-decker bus crashed into a bus stop in Stockholm on Friday, killing three people and injuring three others, police said.

Authorities were alerted to the crash at 3:23 p.m. on Friday. The vehicle rammed into the bus shelter on Valhallavägen, a street in the Swedish capital’s Östermalm district. The area is in the northern part of the city, near the Royal Institute of Technology.

Police were treating the crash as “involuntary manslaughter” but were still investigating. It wasn't immediately clear what the cause was.

Swedish news agency TT said police confirmed that the driver had been detained and would be questioned to determine what happened. The front of the bus appeared to be have been seriously damaged.

Emergency services said the vehicle — a regular city bus — was not in service and no passengers were on board at the time, TT reported.

Prime Minister Ulf Kristersson wrote on X he had “received the tragic news that several people have been killed and injured at a bus stop ... People who were perhaps on their way home to family, friends, or a quiet evening at home.”

He said that “we do not yet know the cause of this, but right now my thoughts are primarily with those who have been affected and their families.”