A woman in her 20s has died in a car crash after a police pursuit by officers investigating a drone that was being flown near prison grounds.
Police were called to Groom Crescent near Wandsworth Prison in south London just after 3am on Tuesday, and began following a car that they saw driving away.
At around 3.10am the car crashed in Ashcombe Street at the junction of Wandsworth Bridge Road, and the woman passenger was pronounced dead at the scene.
The driver, a man also thought to be in his 20s, is in a critical condition in hospital. Police are in the process of telling their families.
Watchdog the Independent Police Complaints Commission is investigating.
Authorities have grown increasingly concerned about the use of drones to smuggle drugs and mobile phones into jails.
Figures obtained earlier this year by the Press Association showed that in 2013 none of the gadgets were discovered in or around prisons in England and Wales. But in 2014 this rose to two incidents, rising to 33 in 2015.
An IPCC spokeswoman said: "The IPCC is independently investigating police actions prior to a fatal road traffic incident in south London in the early hours of Tuesday 9 August in which a woman has died and a man has been critically injured.
"The Metropolitan Police referred the matter to the IPCC because a police vehicle was following the car involved in the collision immediately prior to the incident.
"IPCC investigators attended the scene and also the post-incident procedures where the officers involved are providing their accounts. The investigation is in its early stages."
A Prison Service spokeswoman said: "On Tuesday August 9, staff at HMP Wandsworth alerted the Metropolitan Police to a drone flying in close proximity to the prison, as is standard practice.
"Police investigations are now under way and it would be inappropriate to comment further."