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.

“Hope is the last thing you lose,” said Valeria Cardona Torres, a 26-year-old volunteer rescuer searching for two cousins believed trapped in a collapsed building in Cali.

“We haven’t found them. We have indications of where they might be, but there are no signs of life.”

The missing pair include the mother of baby Salomon, who was pulled alive from the rubble on the first day alongside his father, who suffered a broken leg.

“We are anxious about hearing news that we do not want to hear,” said the young rescue worker.

Thursday morning marks 72 hours since the quake, a period when survivors are considered most likely to be found alive, unless they are near pockets of water and air.

Several dozen aftershocks and widespread structural damage were complicating the rescue effort.

“We are making progress,” said Juan Diego Patino, governor of nearby Risaralda province. “But day after day the buildings that were left on the verge of collapse, some of them are now collapsing.”

Colombia’s new president, Abelardo de la Espriella, has declared the disaster an “economic emergency” and announced three days of national mourning.

“We will do what is necessary,” he said in a statement, vowing to “emerge again as a country and as a society.”

More than 11,000 dwellings have been destroyed and thousands of families have been rendered homeless, according to official figures.

But the toll may yet be higher, with some remote communities near the Pacific coast yet to be surveyed.

Ombudsman Iris Marin said a hospital in Choco was operating at 160 percent capacity and that authorities had yet to verify conditions in 32 Indigenous settlements.

-‘My house is finished’ –

Many families have already spent consecutive nights outdoors, either because their homes were damaged or they feared aftershocks.

Javier Alzate, a 79-year-old psychologist, was trying to remove tiles and other dangerous bits of debris so he could get access to his damaged home.

“There’s no other option. We have to get everything out because if it rains, everything will be ruined,” he said.

“It’s very distressing. Very sad. You work 40 or 50 years to buy a little house, struggling all that time to get it. I finally got it, and a few days later it’s gone.”

“My house is finished. I lost my home and my car.”

Dilian Francisca Toro, governor of Valle del Cauca, said officials were conducting a census of damaged and destroyed homes to determine which buildings could still be occupied.

“We have to begin working because people simply cannot bear staying out on the streets any longer,” she said.

“People are telling us: ‘If you give us the materials, we’ll do the work ourselves,'” Toro said, describing plans for community-led reconstruction efforts.

Many Colombians have mobilized to help, bringing water, food and supplies to affected neighborhoods, while long lines formed outside blood donation centers.

Colombia was also preparing to receive international urban search-and-rescue teams from the United States, El Salvador, Ecuador and Israel, according to disaster authorities.