U.S. Secretary of State Rex Tillerson delivers remarks at the morning ministerial plenary for the Global Coalition working to Defeat ISIS at the State Department in Washington, March 22, 2017. Reuters

Secretary of State Rex Tillerson ordered a “mandatory social media check” on anyone applying for a U.S. visa who had ever visited a country or territory where the Islamic State group operated, Reuters reported Thursday.

The social media checks were included in the most recent of four memos Tillerson issued in the past two weeks, instructing immigration officials on how to implement “extreme vetting” of foreigners entering the U.S. under President Donald Trump. The memos had been unreported until Reuters obtained copies of them earlier this week. The last of the memos was issued Friday.

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The fourth memo could explain reports saying U.S. customs officials were asking foreigners to hand over their cellphones and provide passwords to their Twitter and Facebook accounts. But the practice was "rarely" performed by consular officials as it led to significant delays in processing visa applications, one former official who wished to remain anonymous, told Reuters.

In the two earlier memos dated March 10 and March 15, Tillerson instructed customs officials on how to enforce Trump’s second executive order banning citizens from six Muslim nations from traveling to the U.S. Those memos told officers to ask specific questions of visa applicants from Iran, Libya, Somalia, Sudan, Syria and Yemen, in addition to forcing applicants to disclose every cell number, email address and social media handle they had used in the past five years. Tillerson rescinded those two memos March 16, the same day a federal court in Hawaii struck down Trump's travel ban for illegally discriminating against Muslims under the First Amendment of the Constitution. Consequently, Tillerson issued memos March 16 and Friday explicitly instructing consular officials not to ask these questions of visa applicants from the six Muslim countries.

In addition to the social media check, the wording of the Friday memo was tailored to instruct border officials to identify “populations warranting increased scrutiny," without singling out citizens of specific Muslim countries.

Nearly 49 percent of Americans "strongly" or "somewhat " agree with Trump's travel ban while 41 percent "strongly" or "somewhat" opposed it, according to a Reuters/Ipsos poll from December 2016. But the responses varied along party lines, with 51 percent of Republicans saying they "strongly" approved, compared to 53 percent of Democrats who said they "strongly" disagreed."