Firefighters and rescue workers stand amidst the rubble of destroyed houses after the explosion of a gas tanker truck in San Pedro Xalostoc, on the outskirts of Mexico City May 7, 2013. A gas tanker truck exploded on a highway north of Mexico City early on Tuesday, killing at least 22 people and injuring more than 30 as a fireball tore through cars and homes. [Photo/Agencies]