Trump earlier in the day announced that he dispatched Secretary of State Michael Pompeo to Saudi Arabia to meet with King Salman bin Abdulaziz and suggested that "rogue killers" might be behind Khashoggi's disappearance in Turkey.
Trump compared the case of Khashoggi, who Turkish officials have said was murdered in the Saudis' Istanbul consulate, to the allegations of sexual assault levelled against Supreme Court Justice Brett Kavanaugh during his confirmation hearing.
But late yesterday evening - after Turkish authorities placed high iron barriers in front of the consulate - a motorcade of six cars drew up and Turkish police and prosecutors entered the premises. Members of US Congress, including South Carolina Republican Senator Lindsey Graham and Democratic Senator Chris Murphy, have called for a change to Washington-Riyadh relations if the Saudi government is indeed responsible for Khashoggi's death.
Saudi Arabia's Arab allies have rushed to its support. Saudi Arabia did not immediately acknowledge he had left or offer a reason for his departure.
The case has provoked an worldwide outcry against Saudi Arabia, the world's top oil exporter, with more media and business executives pulling out of a planned investment conference there this month.
Trump sent Secretary of State Mike Pompeo to Riyadh to talk directly with Saudi Arabia's royals amid strong pressure in Congress and the U.S. media to prevent the vanishing of Khashoggi from being swept under the carpet.
The Glazers sold two per cent of the club's shares with limited voting rights in August past year, and may be interested in selling more to the Saudis.
Speaking on Monday, Mr Trump said Saudi leader King Salman denied "any knowledge of whatever may have happened" during a phone call.
The secretary added that he emphasized the importance of conducting a thorough, transparent, and timely investigation, and the Saudi leadership pledged to deliver precisely on that.
"Answers will be forthcoming shortly", Trump added. Democratic lawmakers criticized Trump for using the term "rogue killers".
Gardiner says Iran, a regional rival to Saudi Arabia, comes into play as well.
"This guy has got to go", said Senator Lindsey Graham, a Republican from SC, speaking on Fox television.
The recent, highly charged exchange of words between Washington and Riyadh now appears to have given way to a mutual search for the least bad explanation.
"We hope this joint investigation will help in removing all speculations", Foreign Minister AH Mahmood Ali said replying to a question on Monday at a briefing ahead of Prime Minister Sheikh Hasina's Saudi visit from Tuesday. "We're going to try get to the bottom of it very soon, but his was a flat denial".
"And sometimes it's important to take a public stand".
The case has strained U.S. -Saudi ties and cast a shadow over Crown Prince Mohammed bin Salman's efforts to overhaul the kingdom's economy and attract foreign investment.
What is the state of investigation?
Turkish police on Monday night undertook an eight-hour search at the consulate, taking away soil and DNA samples, although a search expected on Tuesday at the consul's residence has so far not taken place.
Turkish officials allege they carried a 15-man Saudi hit squad, while pro-Saudi media claims they were simply tourists. What evidence Turkish officials could gather at the consulate remained unknown.
Turkish security sources have long made clear they have audio evidence pointing to his murder.
Pompeo will fly to Ankara on Wednesday for talks with Turkish officials about the case.
What is alleged to have happened at the consulate?
The newspaper said Khashoggi, a Washington Post contributor, was then decapitated.