Jordan's Islamist opposition on April 19 denounced the presence of U.S. troops in Jordan, AFP reported.

Massachusetts Institute of Technology in Boston issued an emergency alert at 10:48 p.m. April 18 reporting that shots had been fired, that an officer was down and that a shooter was at large, Daily Mail reported.

The FBI on April 18 released photos and surveillance video on its website of two men the bureau considers suspects in the April 15 Boston Marathon bombings.

The presidents of Argentina, Brazil, Ecuador and Uruguay have confirmed their participation in an urgent meeting of the Union of South American Nations, also known as UNASUR, in Peru on April 18 to express support for Venezuelan President-elect Nicolas Maduro, MercoPress reported.

Between five and 15 people were killed when an explosion occurred at a fertilizer plant in the Texas town of West, some 130 kilometers (80 miles) south of Dallas, late on April 17, Reuters reported April 18, citing police

A law enforcement official said April 17 that U.S. authorities arrested a suspect in connection to the letters sent to U.S. President Barack Obama and Sen. Roger Wicker that tested positive for the poison ricin, Reuters reported.

A U.S. unmanned aerial vehicle strike in southern Yemen on April 17 killed an al Qaeda in the Arabian Peninsula leader, identified as Hamid al-Radmi, and four other militants, an unnamed Yemeni government official said, Reuters reported.

The Pentagon is sending approximately 200 troops from the Army's 1st Armored Division to Jordan to help contain violence along the Syrian border and plan for any operations needed to ensure the safety of chemical weapons in Syria, U.S. Defense Secretary Chuck Hagel said April 17, AP reported.