21.   Officials suspected a gas leak triggered the blast on Thursday.

22.   Officials suspected a liquified petroleum gas leak triggered the blast, which buried motorists in cars, toppled utility poles and smashed windows and storefronts for blocks around.

23.   The blast was triggered by remote control, Sandoval added.

24.   The local Afghan commander blames a rocket attack for triggering the blast.

25.   The latest theory has focused on a torpedo exploding inside the submarine, but it is still unclear what triggered that blast.

26.   The local Afghan commander blamed a rocket attack for triggering the blast.

27.   The U.S. Embassy said a car bomb apparently triggered the blasts.

28.   The U.S. Embassy said a car bomb triggered the blasts.

29.   Toledo said a gas leak apparently triggered the blast at the Humberto Vidal shoe store in Rio Piedras, a residential and shopping district in San Juan.

30.   Toledo said a natural gas leak apparently triggered the blast at the Humberto Vidal shoe store in Rio Piedras, a residential and shopping district in San Juan.