One car caught fire following the crash, but the flames were quickly extinguished.
The first collision occurred when the bus was making a turn onto Allégatan and ran into one car.
After the crash however, witnesses reported that the bus continued moving, picking up speed along the way.
The bus ended up running into eleven vehicles before the driver steered the bus away from the scene.
By then he had informed his dispatcher about the accident.
“He was probably in such a state of shock that he didn’t realize what he was doing," said police spokesperson Lars Hullegård to the TT news agency.
"The driver claims the gas pedal was stuck. The bus will be examined on Monday, so until then we won’t really know what caused the accident,”
The accident resulted in the street being completely blocked and caused what was described as a chaotic scene, with several ambulances also descending on the area.
The driver was tested for alcohol, but no traces were found in his blood.