The United States has told its diplomats overseas to identify groupswhose members should be thoroughly investigated when they request a visa.The State Department sent a series of directives to U.S. embassiesand diplomatic offices earlier this month.The department told them to investigate the social media messagesand activities of visa applicants.It said officials should be looking for people who are suspected of terrorist tiesor of having been in areas controlled by the Islamic State group.Another directive ordered embassies to set up securityand intelligence working groups to establish guidance for "population sets."It said these measures would identify which people require a detailed investigationbefore they are permitted in the United States.Even if someone is qualified for a visa,they could still be barred from entering the countryif they do not meet the rules set by the working groups.The directives are the first evidence of a Trump administration planfor the "extreme vetting" of foreigners before they are given visas.Before becoming president, Donald Trump promised such a planto American voters during the 2016 election campaign.The four documents sent between March 10 and March 17do not tell which "population sets" are to be given additional examination.But one document says investigators should ask visa applicantsabout where they worked, who they worked forand where they traveled over the past 15 years.The document also tells investigators to ask applicants for all email addressesand social media names used over the past five years.The State Department said later it was withdrawing the questionsuntil they are approved by another federal agency.The Reuters news agency first reported on the series of directives last week.Rights groups and others have criticized the directivesand accused Trump of discriminating against Muslims.They note his recent executive order to block travelers from six countries:Iran, Libya, Somalia, Sudan, Syria and Yemen.A federal judge has suspended the government's enforcement of the ban.The rights group Amnesty International wrote a letterto Secretary of State Rex Tillerson last week.It said the documents "could provide license for discriminationbased on national origin and religion.They could provide a pretext for barring individualsbased on their nonviolent beliefs and expression.Social media checks, as well as demands for social media passwords at U.S. borders,have significant implications for privacy and freedom of expression."Law professor Anil Kalhan leads the international human rights committeeof the New York City Bar Association.He said the documents "will needlessly worsen visa processing backlogs"and may lead to applications for visas being wrongly denied.Some refugee aid groups and even State Department workershave said the visa investigation process is already very strong.Stephen Yale-Loehr is an immigration law professor at Cornell University's law school.Last month, he told CBS News "we have a terrorist watch database.We have known immigration violators database.We have a criminal background check database that they have to go through.They don't just take the visa applicant's word.They do go through all of these computer databases to verify for themselvesthat it's appropriate to issue the visa to a particular individual."