“It was her view that the bus lurched forward, and when she tried to stop it the brakes didn’t work at all,” said Maria Eklund at Södermalm police station.

Six people were injured on Saturday when the 15-year-old bus, which had been taken in for repairs earlier in the week, veered off the road and into a square at Slussen in central Stockholm.

The driver lost control of the number 55 bus bound for Sofia as she attempted to pull in at a bus stop. Instead the vehicle rolled down a set of steps and into a crowd of pedestrians at the busy Södermalmstorg square.

”We have lots of witnesses and many of them are very shocked by what they saw,” said police inspector Stefan Färdigs.

One man was seriously injured when the bus careered into the crowded square. His injuries are not believed to be life-threatening. Five others, including a 17-month-old-child, were treated for minor injuries. The child’s stroller was crushed by the vehicle before the bus came to a halt at the steps leading to the Stockholm City Museum.

A reporter for news agency TT said the square “resembled a war zone” immediately after the accident.

Stockholm’s streets were crowded at the time as people thronged to catch sight of the runners in Saturday’s Stockholm marathon.

Tests showed that the driver was not under the influence of alcohol.

“The bus driver is in shock and was taken to hospital but does not have any physical injuries. She has been driving with us for more than ten years,” said Martin Hägglund at Keolis Sverige, a transport company that operates services for the Stockholm public transport system.

Hägglund said the bus had been in for repairs three days earlier due to a faulty brake pedal.

“But it’s hard to see that there might be a connection with this accident. Buses are regularly taken in for repairs.”

The 15-year-old Scania bus was inspected and serviced in mid-April. It was scheduled to be taken out of service later this year since 15 years is the upper age limit for buses plying routes in the Stockholm region.

Bengt Bryungs, chair of the transport section at the Swedish Municipal Workers Union (Kommunal), praised Keolis’ track record and said the age of the bus should not matter unduly if the vehicle was well maintained.

“They have a very good service level and a high level of safety. My impression is that they maintain a good standard,” said Bryungs.

A second driver who operated the bus earlier in the day said there had been no problems with the vehicle.

Stockholm police have indicated that they will conduct a full examination of the vehicle and question the driver as they investigate the cause of the accident.