Covered in mud, 38-year-old Marta Gomez told of going to search for her missing niece -- and making a chilling find instead.
"I went to look for my niece, but I couldn't find her. I dug and dug and found what turned out to be a baby's hand. It was horrible," she said in a shelter set up for the newly homeless.
As she stood in line waiting to register for government assistance for those who lost their houses, she told AFP she had given up on finding her niece.
"The mud took her away. I'll never see her again," she said, clinging to the leash of her equally muddy German shepherd.
President Juan Manuel Santos was in the southern town personally overseeing the relief effort.
Watch: Colombia Mudslides leave more than 250 people dead
He said in a national address that the death toll had risen to 254 people, including 43 children.
"We offer our prayers for all of them. We send our condolences and the entire country's sympathies to their families," he said.
Currently, no one has officially been reported missing, he said.
Earlier reports had said more than 100 people were unaccounted for. But that figure apparently fell as authorities identified the dead.
Rescuers worked in stifling heat under a cloudy sky in the remote town in the Amazon basin, the capital of Putumayo department.
The debris left by the mudslides was everywhere: buried cars, uprooted trees, children's toys and stray shoes sticking up out of the mud.
Pope's prayers
The torrent of mud, boulders and debris struck the town with little warning late Friday after days of heavy rains that caused three area rivers to flood.
It swept away homes, bridges, vehicles and trees, leaving piles of wrecked timber.
Most of the hardest-hit neighborhoods in the town of 40,000 are poor and populated with people uprooted during Colombia's five-decade-long civil war.
A "profoundly saddened" Pope Francis said he was praying for the victims.
Santos declared an emergency to speed up aid operations.
Health authorities dispatched sanitation specialists in hopes of preventing outbreaks of disease.
'People screamed, others cried'
Marta Ceballos, a 44-year-old street vendor, said she lost everything, but is thankful her family is alive.
"Dear God, I don't want to even remember that," she said.
"To see how some people screamed, and others cried, ran, tried to flee in cars, on motorcycles, and how they were trapped in the mud. It's all too, too difficult," she told AFP.
"The only things I fortunately did not lose were my husband, my daughters and my nephews," she said.
Soldiers carry a victim, in Mocoa, Colombia. (AAP) Source: AAP
'Unprecedented tragedy'
Electricity and running water have yet to be restored to Mocoa. Local authorities said repairing the electrical substation would take time.
There were reports of people looting stores searching for bottled water.
"There are lots of people in the streets, lots of people displaced and many houses have collapsed," retired Mocoa resident Hernando Rodriguez, 69, said by telephone.
"People do not know what to do... there were no preparations" for such a disaster, he said.
Several deadly landslides have struck Colombia in recent months.
A landslide in November killed nine people in the rural southwestern town of El Tambo, officials said.
The previous month, 10 people lost their lives in a mudslide in the north of the country.
The Pacific rim of South America has been hard hit in recent months by floods and mudslides, with scores killed in Peru and Ecuador.
Climate change can play a big role in the scale of such natural disasters, a senior UN official said.
"Climate change is generating dynamics and we see the tremendous results in terms of intensity, frequency and magnitude of these natural effects, as we have just seen in Mocoa," said Martin Santiago, UN chief for Colombia.
Watch: Historic flooding in Peru
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