A bus driver has been arrested on suspicion of driving under the influence of drugs after a double-decker bus collided with two vehicles and hit a bus shelter in south London, leaving a teenage girl in a critical condition and injuring 19 other people.

The 198 Arriva bus collided with a car and a single-decker bus and crashed into a shelter at West Croydon bus station after mounting the pavement at around 12:20pm on Sunday.

A Metropolitan police spokesperson said: “A girl, believed aged 15 and a passenger on the route 198 bus, was treated at the scene for injuries before being taken to a south-London hospital. She remains there in a critical condition. Her next of kin have been informed. A number of other people were treated at the scene for minor injuries.”

Bus crashes into West Croydon bus station.. 😳 pic.twitter.com/ETADofbb9P — Aylin ❤︎ (@aaylinyilmaaz) November 11, 2018

It was also confirmed that the driver, a man, remains in police custody after failing a roadside drugs screening test.

London ambulance service said that there were 20 casualties with varying degrees of injury, 18 of which were admitted to hospital.

A TfL spokesperson said: “We are aware of an incident involving a route 198 bus at West Croydon bus station. We are supporting the emergency services and will work with them and with the operator, Arriva, in their investigation into this incident.”

Croydon police force tweeted: “Officers are responding to bus in collision with street furniture in Station Road, Croydon by West Croydon bus station. One woman being treated at scene. Temporary road closures. No other serious injuries.”

Final information about our response to the bus collision

in Croydon, following which we treated 20 patients and took 18 of them to

hospital. pic.twitter.com/P1da81MCCE — London Ambulance (@Ldn_Ambulance) November 11, 2018

Eight ambulance crews, a hazardous area response team, a motorcycle paramedic, paramedics and London’s air ambulance attended the scene, as well as dozens of other emergency service workers.

Pictures circulated on social media showed debris strewn across the street, with the front of the bus crumpled into a small wall.