An Afghan fireman stands next to the debris of a car at the scene where a suicide car bomber attacked a NATO convoy in Kabul, Afghanistan, on May 16.

A U. S soldier secures the area where a suicide car bomber attacked a NATO convoy in Kabul on May 16.

A U.S. soldier arrives at the scene where a suicide car bomber attacked a NATO convoy in Kabul on May 16.

An Afghan man directs his children away from the scene of the attack.

The mother of 22-year-old Ayten Calim mourns during her funeral in the town of Reyhanli in Hatay province, Turkey, near the Turkish-Syrian border on May 14. Calim was one of around 50 people to have been killed by two bomb attacks in Reyhanli over the weekend.

Relatives cover the body of 22-year-old Ayten Calim with a Muslim prayer rug and her wedding dress as they lower her into a grave in the town of Reyhanli in Hatay province, Turkey, near the Turkish-Syrian border on May 14.

People stand in a damaged building on May 14, at Reyhanli in Hatay, Turkey, just a few miles from the main border crossing into Syria. The death toll in twin car bombings in a Turkish town near the Syrian border has increased to 50 after another body was recovered and a victim died in hospital, the health minister was quoted as saying on May 14. The attacks also provoked a backlash against the nearly 400,000 Syrian refugees in Turkey. Government officials have repeatedly warned against provocations and said Turkey will maintain its open-door policy for Syrians fleeing the regime's crackdown.

A man works in a damaged building on May 14 at Reyhanli in Hatay, Turkey, just a few miles from the main border crossing into Syria.

An injured woman is pictured after an explosion in Prague April 29. The explosion in central Prague on Monday injured about a dozen people and others were trapped in a building damaged by the blast, a Reuters witness and emergency services officials said.

A firefighter inspects the scene of an explosion on April 29, in Prague, Czech Republic. At least 40 people were injured in the large explosion at a Film and TV school building on the Smetana embankment.

Firefighters search the area after an explosion in Prague April 29. The explosion in central Prague on Monday injured about a dozen people and others were trapped in a building damaged by the blast, a Reuters witness and emergency services officials said.

Firefighters stand at attention as mourners applaud a West, Texas fire engine during a processional before the start of a memorial service honoring those killed in the West, Texas fertilizer plant explosion at the Ferrell Center on the Baylor University campus in Waco, Texas on Thursday.

Members of the Patriot Guard line the road for a procession in Waco prior to a memorial service for first responders who died in last week's fertilizer plant explosion in West, Texas.

An honor guard stand in front of caskets prior to a memorial service in Waco, Texas for first responders who died in last week's fertilizer plant explosion in the small town of West.

President Barack Obama and first lady Michelle Obama bow their heads behind a photo of volunteer firefighter Capt. Cyrus Adam Reed, who was killed, as they attend the memorial for victims of the fertilizer plant explosion in West, Texas at Baylor University in Waco.

The damage from the fertilizer plant explosion is seen from helicopters in accompanying President Barack Obama in West, Texas, en route to Baylor University, where the president was to speak at a memorial service.

This Thursday, April 18, 2013 aerial photo shows the remains of a nursing home, left, apartment complex, center, and fertilizer plant, right, destroyed by an explosion in West, Texas.

This aerial photo shows the remains of a burned and damaged school following a Wednesday night fertilizer plant explosion in West, Texas, Thursday, April 18.

Police and rescue workers stand near a building which was left destroyed from a massive explosion at a nearby fertilizer plant in the town of West, near Waco, Texas April 18.

Investigators stand amid the aftermath of a massive explosion at a fertilizer plant in the town of West, near Waco, Texas April 18.

This aerial photo shows burned down and damaged homes on Thursday, April 18 following an explosion Wednesday a near by fertilizer plant in West, Texas,

In this Instagram photo provided by Andy Bartee, a plume of smoke rises from a fertilizer plant fire in West, Texas on April 17, 2013.

General view inside the damaged building of state-owned Mexican oil giant Pemex in Mexico City, Mexico.

Firefighters belonging to the Tacubaya sector and workers dig for survivors after an explosion at an adjacent building to the executive tower of Mexico's state-owned oil company PEMEX, in Mexico City, Thursday Jan. 31, 2013. A large explosion occurred in the lower floors of the building.

An injured person is transported on a stretcher the headquarters of state oil giant Pemex in Mexico City Jan. 31.

Rescue workers head for the skyscraper.

A helicopter overflies the area following a blast inside the skyscraper that houses the headquarters of state-owned Mexican oil giant Pemex.

Firefighters work the scene where an explosion has killed two people and damaged more than a dozen homes in the Richmond Hill subdivision, late Saturday, Nov. 10, in Indianapolis, Ind.

People walk among rubble at the site of a fuel truck explosion in Riyadh, Saudi Arabia, on Nov. 1, 2012. A fuel truck exploded after hitting portions of a bridge, engulfing buildings and cars in flames, witnesses and officials said.

An injured man lies on a stretcher after an explosion in eastern Riyadh on November 1, 2012.

People walk among debris at the site of a fuel truck explosion in Riyadh on Nov. 1, 2012.