A 77-year-old woman has died after being hit by a bus near Tooting Broadway Tube station on Friday.
The Met said its Serious Collision Investigation Unit was investigating the incident.
Officers have appealed for those with dash cam or mobile phone footage to contact police.
The Air Ambulance and London Ambulance Service were called to the scene.
The incident temporarily closed the major road in both directions while Garratt Lane, which connects Tooting to Earlsfield, was also temporarily reduced to one lane westbound.
A London Ambulance Service spokesperson said after the collision: "Our first medics arrived on scene in around three minutes.
“We treated a woman at the scene for a head injury and took her to a major trauma centre as a priority.”
Anyone with footage is asked to contact police by calling 101 or Tweet @MetCC on 'X' quoting 3044/3NOV.