Two women who died in a collision with an unmarked police car responding to a 999 call have been named.
Ann Valley, 87, and Gwyneth DeCamps, 88, both from Slough, were in a Nissan Micra when the crash happened on the A4 in Calcot, Reading.
The Independent Office for Police Conduct (IOPC) is investigating and says the police car had its blue lights on at the time.
It has appealed for witnesses to the incident on 23 January to come forward.
The watchdog's investigators are analysing the police vehicle's on-board incident data recorder, which records the car's speed and movements.
Sarah Green, of the IOPC, said: "My thoughts are with all of those affected by this tragic event.
"Our family liaison manager has met the families of Mrs Valley and Mrs DeCamps to offer our condolences and to tell them about our role and our investigation."
Witnesses are asked to email firstname.lastname@example.org or to call 0800 096 9077.