Investigators want to trace a woman they believe was an off-duty nurse at the Hillsborough tragedy.
She is among potential witnesses thought to have helped some of the 96 Liverpool fans who died at the FA Cup semi-final on April 15 1989.
The woman is believed to have assisted casualties placed in the back of a South Yorkshire Metropolitan ambulance when it was parked on the pitch in front of the West Stand terrace at the Leppings Lane end.
The witness, thought to be from the Nottingham area, then travelled in the back of the ambulance to Sheffield’s Northern General Hospital.
An image of the ambulance, timed at 15:36.59, has been released.
Images of other witnesses have also been released by Operation Resolve on behalf of Hillsborough inquests coroner Sir John Goldring.
Operation Resolve was set up by Home Secretary Theresa May to investigate whether any individuals or organisations are criminally culpable for their part in the disaster.
The public are asked to visit www.operationresolve.co.uk to view the gallery of pictures and call 08000 283284 if they identify an image