Detectives from the Serious Collision Investigation Unit are appealing for witnesses and those with dash cam footage to come forward following the incident.
Police were called at 4.50am after a vehicle collided with a residential block in Great Western Road, Westminster W9.
Police, London Fire Brigade and London Ambulance Service paramedics attended the scene and found the vehicle alight.
The LFB extinguished the fire but, despite the best efforts of emergency services, three people were pronounced dead at the scene.
Work to identify the deceased and inform their next of kin is ongoing.
There are not believed to be any other injuries and at this stage no other vehicles are believed to have been involved.
A number of residents were evacuated from the building as a precaution.
A scene remains in place and enquiries are ongoing.
Anyone who saw the car before the incident, or who has information, video or images that could help police, is urged to call 101 ref CAD 917/14 Sept.