Flying back home, Pompeo remained positive about an ongoing Saudi probe into Khashoggi's disappearance, but stressed answers need to come soon.
U.S. Treasury Secretary Steven Mnuchin on Thursday said he would no longer attend next week's investment conference in Saudi Arabia over the disappearance of Washington Post journalist Jamal Khashoggi. "You're going to get me in trouble".
"This is the last piece of his I will edit for The [Washington] Post".
Crime scene investigators concluded a second search of the consulate and the consul's residence overnight Thursday.
Image: Mr Khashoggi entering the Saudi consulate in Istanbul on 2 October.
Turkish government sources have claimed that Mr Khashoggi - a critic of the government in Riyadh - was murdered during a visit to the Saudi consulate in Istanbul two weeks ago. Turkish authorities suspect he was abducted and murdered by the Saudis.
Earlier this week, Pompeo was dispatched to Riyadh, where he met Saudi King Salman and bin Salman in Riyadh to discuss the Khashoggi case.
The Post initially held off on publishing the column amid hope for Khashoggi's return, Attiah said. But on Wednesday, Trump told reporters: "We've asked for it ... if it exists" - before adding that it "probably does" exist. Saudi Arabia denies killing him.
The New York Times said it confirmed that at least nine of the 15 worked for the Saudi security services, military or other government ministries.
In his brief comments to reporters, Pompeo also stressed the "longstanding strategic relationship" between the US and Saudi Arabia.
President Donald Trump's previous warnings over the case drew an angry response Sunday from Saudi Arabia and its state-linked media, including a suggestion that Riyadh could wield its oil production as a weapon.
Turkish forensic officials arrive to the residence of Saudi Arabia's Consul General Mohammad al-Otaibi in Istanbul, Oct. 17, 2018.
Turkish sources said the authorities have an audio recording but Ankara has not shared the graphic evidence with USA or European allies who are also investigating Khashoggi's disappearance.
Forensic teams had already visited the consulate once this week, going there Monday to search for clues to what happened to Khashoggi after he entered the diplomatic outpost on October 2.
It said Otaibi can be heard on one tape saying during Khashoggi's torture: "Do this outside".
Media captionCCTV footage shows missing Saudi journalist Jamal Khashoggi entering the Saudi consulate in Istanbul.
On Tuesday, G7 foreign ministers called for Saudi Arabia to conduct a "transparent" investigation into the issue.
In an interview with Fox News, a prominent Trump ally in the Senate called on Saudi Arabia to reject the crown prince, known as MBS, who rose to power previous year and has aggressively sought to soften the kingdom's image overseas and attract foreign investment.
Meanwhile, International Trade Minister Liam Fox has been told to pull out of a business conference in Saudi Arabia next week as finance ministers from France and the Netherlands and prominent banking executives have scrapped their plans to attend.