Khashoggi, a Saudi national and US resident who became increasingly critical of powerful Crown Prince Mohammed bin Salman, has not been seen since he walked into the Saudi consulate in Istanbul to sort out marriage paperwork on October 2.
Turkish officials have said they believe he was killed — a claim Saudi Arabia refuted — and the controversy has dealt a huge blow to the image of the kingdom and efforts by the youthful crown prince to showcase a reform drive.
Riyadh had so far not allowed the search at the Istanbul consulate — officially Saudi territory — amid reports both sides were at odds over the conditions of the probe.
But a Turkish diplomatic source said it was expected that the search, a joint operation with Saudi authorities, would “take place towards the evening” Monday.
Dozens of media organisations — some of whom had set up tents — were maintaining a constant vigil outside the consulate in expectation of the search finally beginning.
Cleaners were seen going into the building around lunchtime, causing a minor flurry of excitement, an AFP reporter said.
The Saudi delegation that was due to be involved in the search and has been in Turkey since Friday arrived at Istanbul police headquarters, Turkish television said.