US Secretary of State Mike Pompeo met with Saudi Crown Prince Mohammed bin Salman in Riyadh on Tuesday to discuss the missing journalist Khashoggi, the Saudi-owned al-Arabiya TV reports.
Earlier in the day, the US top diplomat had a meeting with Saudi King Salman and Saudi Foreign Minister Adel al-Jubeir, who agreed on the need for a "thorough" investigation into Khashoggi's disappearance, spokesperson for the State Department Heather Nauert noted in a statement.
Pompeo also thanked King Salman for his commitment to a transparent investigation into the case.
Saudi journalist Jamal Khashoggi, known for his criticism of the government's policies, has been missing since October 2, when he entered the Saudi consulate in Istanbul to obtain a marriage document.
It emerged earlier on Tuesday that police would search the consulate building for toxic substances. The news broke after the joint Saudi-Turkish working group conducted a nine-hour inspection of the Saudi Consulate building on October 15, during which the police reportedly obtained some evidence relevant to the Khashoggi case proving that the journalist never left the building.
Ankara has earlier claimed that Khashoggi could've been arrested or even killed while inside the diplomatic mission, which Riyadh has vehemntly denied. The Saudis insisted that he left the building later the same day and offered Turkish authorities to search the Consulate General building if necessary.
A number of countries have voiced concerns over the case; US President Trump threatened to impose "severe punishment" on Saudi Arabia if it turns out that Riyadh is behind the suspected killing.