"It has been 13 days since the event, so surely proving some of the evidence might be hard, but we believe we will obtain evidence", a Turkish official told Reuters.
If that group is to be characterized as part of a rogue operation meant to bring Khashoggi back to Saudi Arabia alive, questions could arise about Salah Muhammed al-Tubaiqi.
"It is a awful situation".
After President Donald Trump played canary in the coal mine for them, the Saudi royal family is getting ready to acknowledge this evening that Washington Post columnist Jamal Khashoggi was killed in the Saudi consulate in Istanbul during an interrogation/kidnap gone wrong.
Turkish President, Recep Tayyip Erdogan, said that he was personally overseeing the investigation into the investigation of Khashoggi's disappearance and insisted that the journalist never left the Saudi consulate.
President Donald Trump has said he has spoken with Saudi Arabia's king, who "denies any knowledge" of what happened to the Saudi journalist who disappeared after entering the kingdom's consulate in Istanbul last week.
Trump said King Salman added that Crown Prince Mohammed bin Salman also "had no knowledge" about Khashoggi's fate.
"I don't think any of our government officials should be going and pretending it's business as usual until we know exactly what's happened here", Rubio said.
Khashoggi, a Washington Post contributor who became critical of the Saudi leadership as Crown Prince Prince Mohammed bin Salman rose to power, was last seen entering the consulate on October 2.
The Washington Post reported in recent days that the Turkish government informed US officials it was in possession of video recordings that prove Khashoggi was killed inside the consulate, but have not made them public.
Previously, Saudi authorities had maintained Khashoggi left the consulate the same afternoon of his visit, but provided no evidence to support the claim.
The US State Department also has urged a thorough investigation into the disappearance.
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U.S. politicians have backed the call for tough punitive action against the Saudis, while Germany, France and Britain have jointly called for a "credible investigation" into his disappearance.
President Trump takes questions from reporters in Georgia.
It is not the first time that King Salman has sought to ease tensions surrounding the 33-year-old Prince Mohammed, who has been cultivated by the U.S. but whose reformist credentials are being quickly shredded by the mystery surrounding Khashoggi's fate.
The crown prince, ambitious, aggressive and just 33 in a kingdom long ruled by aging monarchs, has considerable weight in Saudi government actions.
Turkish crime scene investigators have searched the Saudi Consulate in Istanbul over the disappearance and alleged slaying of Saudi writer Jamal Khashoggi.
The impact on relations between the US and Saudi Arabia could be far reaching, if it's found that the Saudis were involved with Khashoggi's disappearance, said Michael Morrell, former acting and deputy director of the Central Intelligence Agency and a CBS national security correspondent, on CBS This Morning. There's something - you'll be surprised to hear me say that.
"His denial to me could not have been stronger", Trump told reporters, referring to the king.
Trump has threatened the kingdom with "severe punishment" if it is shown that Khashoggi was killed inside its Istanbul mission.
U.S. Senator Marco Rubio and Senator Jeff Flake, members of the Foreign Relations Committee, said Congress was prepared to move quickly and firmly if Trump failed to adequately respond to the October 2 disappearance of Khashoggi.
Saudi Arabia has pledged to retaliate economically for any United States punitive action.
"It's being investigated, it's being looked at very, very strongly", Trump said, after CBS's Lesley Stahl asked whether the Saudis had murdered Khashoggi.