• Experts will examine two ossuaries - small chambers where dead are buried - found in the first search.
• Ms Orlandi's family hopes the search at the Vatican's Pontifical Teutonic College holds the key to a mystery that has gripped Italy since 1983.
The Vatican is set to make its latest attempt to unravel the mystery of the disappearance of a teenage Italian girl 36 years ago.
The first attempt on 11 July exhumed two tombs a tip-off had said might contain Emanuela Orlandi's remains.
But it only deepened the mystery as even the bones of two princesses thought to be there were missing.
On Saturday, experts will examine two ossuaries - small chambers where dead are buried - found in the first search.
Ms Orlandi's family hopes the search at the Vatican's Pontifical Teutonic College holds the key to a mystery that has gripped Italy since 1983.
What will happen on Saturday?
The search is still focused on the college, where the first exhumations took place in the graveyard there.
During that search, the two ossuaries were discovered under a trapdoor in the floor of a nearby building.
Forensic scientists will examine any bones that are found and could be able to date them within the space of just five hours - although formal identification by DNA would take a lot longer.
One expert appointed by the Orlandi family will be present.
It is thought relatives of the two German princesses - Sophie von Hohenlohe and Charlotte Federica of Mecklenburg, who died in the 19th Century - had been invited to attend but it was unclear whether they would do so.
The Vatican thinks the bones of the princesses may have been moved during work in the 1960s and 1970s.
What is the Teutonic Cemetery?
Inside the world's smallest state, the Teutonic Cemetery is easy to miss.
The first attempt exhumed two tombs a tip-off said might contain Emanuela Orlandi's remains.The plot of land, located on the original site of the Emperor Nero circus, is tucked away behind high walls in the shadow of St Peter's Basilica.
The cemetery is normally used as a burial ground for German-speaking members of Catholic institutions. Tourists aren't allowed along the path which leads towards the graveyard.
The nearest you can get is a gate protected by a single Swiss Guard.
What happened to Emanuela?
On 22 June 1983, Emanuela was on her way back home from a flute lesson. She was seen at a bus stop in the centre of Rome. Then, she simply vanished. No-one has seen her since.
Decades of speculation have followed. Was she kidnapped and killed? If so, where is her body?
Emanuela's family have had to chase endless leads and rumours.
"Many people tell me, just let it go, enjoy your life, don't think about it anymore," her older brother Pietro told the BBC. "But I can't let go. I couldn't be at peace if this is not solved."
Attention has always focused on the fact that Emanuela was the daughter of a Vatican City employee.
Why focus moved to cemetery
In March 2019, the Orlandi family received an anonymous letter.
It showed a picture of an angel above a tomb in the Vatican's Teutonic Cemetery.
Was this a clue to where Emanuela was buried?
The family knew that it had to approach the Vatican. But it had had no luck with its previous inquiries.
The family made a general request to the Vatican to open the tomb at the Teutonic Cemetery. A Vatican City state tribunal then granted the request.