In this picture taken Thursday, April 14, 2016, a Syrian man carries a carpet as walk through a devastated part of the town of Palmyra as families load their belongings onto a bus in the central Homs province, Syria. Thousands of residents of this ancient town who fled Islamic State rule are returning briefly to check on their homes and salvage what they can – some carpets, blankets, a fridge or a few family mementos. There is no water or electricity in the town, and it will be at least few months before anyone can return to stay. (Photo by Hassan Ammar/AP Photo)

New York Police Department tactical police officers stand guard near the New York Stock Exchange on September 9, 2011 in New York City. Officials are stepping up security in New York and Washington D.C. a day after U.S. officials received a credible but unconfirmed terror threat to utilize car bombs on bridges or tunnels in New York or Washington. (Photo by Justin Sullivan/Getty Images)

One-year-old female giant panda cub Nuan Nuan reacts inside her enclosure during joint birthday celebrations for the panda and its ten-year-old mother Liang Liang at the National Zoo in Kuala Lumpur on August 23, 2016. Giant pandas Liang Liang, aged 10, and her Malaysian-born cub Nuan Nuan, 1, were born on August 23, 2006 and August 18, 2015 respectivetly. (Photo by Mohd Rasfan/AFP Photo)

A girl wearing a mask takes part in a procession celebrating the religious holiday of Mawlid al-Nabi, the birthday of Prophet Mohammad, in Benghazi, Libya December 10, 2016. (Photo by Esam Omran Al-Fetori/Reuters)

People use a board to travel on a flooded street after heavy rainfall in Baghdad, Iraq, October 31 2015. (Photo by Ahmed Saad/Reuters)

The front wheels of a tractor, pulling a trailer overloaded with sugarcane, are seen lifted off the ground as it passes through the streets of Karor Lan Esan, Pakistan December 6, 2015. (Photo by Caren Firouz/Reuters)

A man covered with thermal blanket walks along railway tracks beside an improvised refugee camp on the border line between Macedonia and Serbia near the northern Macedonian village of Tabanovce, Thursday, March 10, 2016. Around 1.500 migrants and refugees are stranded at Tabanovce transit center for refugees in northern Macedonia. (Photo by Boris Grdanoski/AP Photo)