U.S. embassies and consulates throughout the Muslim world will be closed on Sunday and possible for longer. The State Department says it is taking the step "out of an abundance of caution" and wouldn't say if they are receiving direct threats. Members of Congress say there are concerns about an al-Qaida-linked attack. Last year, the U.S. ambassador to Libya was killed in Benghazi, along with three other Americans. At that time, there were also violent protests at U.S. embassies in Cairo and Tunisia.