Search crews in Colombia raised clenched fists to call for silence Thursday as they listened for life beneath the wreckage of a powerful earthquake that has killed at least 265 people and left hundreds missing.The effort was part of last-ditch attempts to locate survivors following Monday’s 7.4-magnitude quake. Humanitarian groups consider the initial 48 to 72 hours the critical window for rescues, though that timeframe can expand if trapped individuals have food and water."There might be two more people alive here, and I’m hopeful," rescuer Daiana Rojas, 25, told The Associated Press. "We have been hearing sounds since 2::green-background[30] a.m., so our hope remains."The effort was part of last-ditch attempts to locate survivors following Monday’s 7.4-magnitude quake (AFP via Getty Images)Rojas and her family escaped unharmed from the strongest quake to strike Colombia this century. She has been volunteering in Cali, among the hardest-hit urban areas alongside Pereira, Manizales, and Quibdó."I thought that was going to be my last moment alive," she recalled. "Seeing this situation in my city breaks my heart."The mayor of Cali, Alejandro Eder, informed journalists Wednesday that teams were still detecting signs of life beneath debris. "The next 20 hours are the most critical to find and rescue people alive," he said.The catastrophe poses an early test for Colombia’s new president, Abelardo de la Espriella, as his administration scrambles to coordinate aid while relief organizations rush assistance to damaged areas.De la Espriella reported Wednesday that nearly 500 individuals remain missing, though civilian-managed records put the figure over 4,200. More than 25,800 families have been impacted, he added.Rojas has seen two survivors pulled alive from the rubble, as well as the recovery of bodies."They are not a relative or a friend of mine, but it feels as they were," she said. "Whenever rescuers ask for silence, everyone stays still and tries not to move, speak or whisper. But when signs of life are found, all the teams start to applaud."