From a mountain of rubble in downtown Pereira, Colombian rescue workers called for silence to listen for sounds of life beneath their feet.

In a plaza full of families who slept outside after Monday’s devastating earthquake, voices drop to whispers, machinery goes silent and the frantic activity of dozens of volunteers pauses. Some onlookers close their eyes and mutter prayers that another survivor will be found with the help of audio equipment trained on a pile of busted concrete and twisted metal.

This routine plays out several times an hour on sites across the historic center of this city of 500,000 people in a coffee-growing region in western Colombia. It’s among the places hardest hit by the magnitude 7.4 quake. Occasionally, cheers go up when another survivor is found.