CALI, Colombia (AFP)—Rescuers in Colombia made a last-ditch effort to locate earthquake survivors early Thursday, as the critical 72-hour window for finding people alive drew to a close.

Some 500 people are still missing after the magnitude 7.4 quake, the strongest to hit Colombia this century, and which has already claimed 265 lives and injured more than 3,500, according to local authorities.

In Cali and Pereira, cities in the country’s west, emergency crews worked for a third night with bare hands, cutting tools and sniffer dogs, stopping only to listen for signs of life.