At least 139 people were killed after a powerful earthquake struck central Mexico, toppling buildings in its populated capital. The Mexico City mayor stated that at least 44 buildings were severely damaged or destroyed in its capital city. The walls of some building sheered off, others just collapsed. Among the damaged were apartment blocks, a school, a factory and a supermarket. Hundreds of volunteers and rescue workers dug through the rubble with picks, shovels and their bare hands. It's the second big quake to hit Mexico this month, striking only hours after many people around the country participated in earthquake drills on the anniversary of the devastating quake that killed thousands in Mexico City in 1985. The powerful 8.1 quake from earlier this month - the strongest to hit the country in 8 decades - left nearly 100 people dead.