The accident occurred shortly after 4 p.m. on Tuesday, according to police.
The bus driver is seriously injured and has been taken by air ambulance to hospital, says police spokesperson Ola Österling.
Four more people have been taken to hospital by ambulance, but police cannot say whether their injuries are serious. In addition, six people have been taken to a local emergency room for check-ups.
A total of 17 people were on the bus when the accident occurred.
"The road curves, and there the bus drove straight into a facade. So far we have no information that suggests there are any pedestrians, that is, any person outside the bus or in the building who has been injured," says Österling.
The police have opened a preliminary investigation into negligence in traffic and causing bodily harm. The bus, which is operated by Nobina, has been seized by police.
According to Nobina's press service, the bus is new and was safety checked last night.
Traffic on the Tvärbanan line has been stopped in both directions at Liljeholmen after the accident.
