A 5-year-old boy was killed on Wednesday afternoon in a collision with a lorry as he crossed St George's Road near Elephant & Castle.
Police and ambulance crews were called at 3.45pm to reports of a collision near the junction with Garden Row.
A 5-year-old boy was pronounced dead at the scene.
"At this early stage it is believed the boy was walking in St George's Road with his mother when he attempted to cross the road," said a Metropolitan Police spokesman.
"As he did so he was in collision with a lorry. The vehicle, described as a flat bed lorry with a crane attachment behind the driver's cab, stopped at the scene."
The driver of the vehicle, a 46-year-old man, was arrested on suspicion of causing death by dangerous driving. He was taken to a south London police station and has been released on bail.
Officers from the road death investigation unit are asking anyone with information to contact them on 020 8285 1574.
Roads were closed after the collision leading to significant traffic jams during the Wednesday evening rush hour.