Turkish officials revealed the existence of the object that may provide important clues into the fate of a Saudi journalist who went missing inside the consulate.
Jamal Khashoggi, a veteran Saudi journalist and newspaper editor, had lived in exile in Washington for more than a year, writing a column for the Washington Post in which he regularly criticised his country's crackdown on dissent, its war in Yemen and sanctions imposed on Qatar.
He said he could write freely in the United States in a way that was impossible at home, according to friends and colleagues, but he was increasingly worried that Riyadh could hurt him or his family.
In Turkey, Mr Khashoggi had friends in high places, including some of President Tayyip Erdogan's advisers.
So when he walked into the Saudi consulate in Istanbul on 2 October, he hoped the appointment would be brief, a simple bureaucratic task that would allow him to marry his Turkish fiancee, whom he had met four months earlier.
"He said the safest country in the world for Saudi Arabians was Turkey," said Yasin Aktay, an Erdogan aide and close friend of Khashoggi.
Turkish officials have said they believe Mr Khashoggi, 59, was killed inside the consulate.
In interviews, Turkish officials provided new details of their investigation into the missing journalist.
Two senior Turkish officials revealed the existence of an object that may provide important clues to Mr Khashoggi's fate: the black Apple watch he was wearing when he entered the consulate.
Outside the consulate, a low rise building at the edge of one of Istanbul's business districts, Mr Khashoggi handed his fiancee his two mobile phones, she told Reuters. He left instructions that she should call Mr Aktay, the Erdogan aide, if he didn't reappear.
Mr Khashoggi was wearing his black Apple Watch, connected to one of the phones, when he entered the building.
A senior Turkish government official and a senior security official said the two inter-connected devices are at the heart of the investigation into Mr Khashoggi's disappearance.
"We have determined that it was on him when he walked into the consulate," the security official said. Investigators are trying to determine what information the watch transmitted.
"Intelligence services, the prosecutor's office and a technology team are working on this. Turkey does not have the watch so we are trying to do it through connected devices," he said.
Tech experts say an Apple Watch can provide data such as location and heart rate. But what investigators can find out depends on the model of watch, whether it was connected to the internet, and whether it is near enough an iPhone to synchronize.
When Mr Khashoggi did not emerge quickly, his fiancee said she at first hoped he had got the document and was talking with consul staff. "But when time passed and employees started leaving the building and he still wasn't out, I panicked," she said.
She called Mr Aktay, the Erdogan aide, and told him her fiance was missing.
As soon as he received the call, Mr Aktay told Reuters, he contacted Turkish security forces and intelligence officials. "
Of course I also called the office of the president, who was in a senior party committee meeting at that point," Mr Aktay said. "After about half an hour, everybody was informed and ready to take the measures needed in this case. And of course then, a long period of tension and expectation started."
Local and international media reported Mr Khashoggi's disappearance the next day. Turkish authorities said there was no evidence to suggest Mr Khashoggi had left the building, and they believed he was still inside. Saudi authorities countered that their citizen had left the consulate and that they were investigating.
Two Turkish security sources told Reuters that security camera recordings showed Mr Khashoggi had not left the consulate by either of its two exits.
Saudi Arabia has strongly rejected the accusation. The kingdom's ambassador to the United States, Prince Khalid bin Salman, said reports suggesting Mr Khashoggi went missing in the Istanbul consulate or that Saudi Arabia had killed him "are absolutely false and baseless" and a product of "malicious leaks and grim rumors."
"Jamal is a Saudi citizen who went missing after leaving the Consulate," the ambassador said in a statement. Saudi Arabia has sent a team of investigators to work with Turkish authorities and "chase every lead to uncover the truth behind his disappearance."
Investigators are also focusing on 15 Saudi men who entered the consulate around the same time as Mr Khashoggi and left a short time later.
Two Turkish security sources said that 15 Saudi men had entered the building at around the time Mr Khashoggi went in, having flown into Istanbul earlier in the day, most of them on a private aircraft from Riyadh and some on commercial flights.
The men left after "some time" in two cars and returned to the airport, the sources said. They said a third vehicle left at the same time but turned in the opposite direction. Investigators are trying to trace its route by analyzing surveillance cameras. The Istanbul consulate referred questions about the 15 men and the vehicles to Saudi authorities, who did not respond to a request for comment.
"It is a very mysterious situation. Diplomats that came in private jets, stay in Turkey for a few hours, and leave. It is also very easy for them to pass through security due to their diplomatic immunity," one of the security sources said.
According to Flight Tracker, an online flight tracking system, a private plane that brought nine of the men in the early hours of Oct. 2 was registered to a company called Sky Prime Aviation Services. A company official confirmed that Sky Prime Aviation owned the plane and that it was in use on Oct. 2, but gave no further details. He said the firm was owned by a private company registered in Saudi Arabia. Two industry sources said the firm belongs to the Saudi government. The Saudi government did not respond to a request for comment.
The other six men arrived on commercial flights, the security source said. The 15 men checked in, briefly, to two hotels, the Movenpick and Wyndham, which are close to the Saudi consulate. The hotels declined to comment.
"It is a very mysterious situation. Diplomats that came in private jets, stay in Turkey for a few hours, and leave. It is also very easy for them to pass through security due to their diplomatic immunity"
As pressure built on Saudi Arabia to locate their missing citizen, Saudi officials in Istanbul showed a Reuters reporter around the consulate on 6 October, opening cupboards and inviting him to inspect the ladies' bathroom. A few hours later, Turkish authorities said they believed Mr Khashoggi had been killed.
A Saudi source told Reuters that British intelligence believed there had been an attempt to drug Mr Khashoggi inside the consulate that culminated in an overdose. He said the information came from a British intelligence source. Contacted by Reuters, British intelligence did not comment. Asked about this account, a Saudi official said: "This death is not true."
Turkish newspaper Sabah said it had identified the 15 as members of a Saudi intelligence team. They included a forensic expert. A Turkish official did not dispute the report.
Investigators are also trying to trace a vehicle that left the Saudi consulate at the same time as two cars destined for the airport, one of the officials said. This vehicle didn't turn toward the airport, but set off in the opposite direction.
This story is based on interviews with Turkish officials, Mr Khashoggi's fiancee and more than a dozen of his friends, who gave insight into the columnist's state of mind in the days leading up to his disappearance, and explained why he went to the Saudi consulate in Istanbul, not the embassy in his adopted home of Washington.
The case threatens to drive wedges between Saudi Arabia and Turkey and between Riyadh and its western allies. US President Donald Trump said on 9 October he plans to speak with Saudi Arabian officials about Mr Khashoggi's disappearance.