STOCKHOLM >> A bus raced out of control down a set of steps and into a busy square after the Stockholm Marathon Saturday, injuring six people and causing a panic among spectators, police and witnesses said.

Police spokesman Stefan Fardigs said five people were seriously injured.

A lot of people were at the square Saturday, following the Stockholm Marathon.

“I heard two bangs and first I thought it was a fight but then I see a bus racing down the stairs step by step,” witness Charlotta Asell told The Associated Press.

Asell, 30, said people screamed and she ran toward a police car parked nearby to get help.

“I put my hands over my eyes,” she said. “I saw it was bad and that people were seriously hurt, but I didn’t want to see it.”

Asell said a stroller lay crushed on the ground, but that the child had escaped without any serious injuries.

Karolinska Hospital said it had received a seriously injured man, two women with lighter injuries and a 1-year-old child with light injuries.

Two people with shoulder injuries were also taken to Stockholm South General Hospital, that hospital said.

Stockholm Public Transport spokeswoman Gunilla Glans said it is unclear what caused the accident and that the bus operator Keolis has started an investigation.

She said the bus driver was also taken to hospital, but had not been hurt.