Rescuers have recovered two bodies from a gold mine where 15 workers are missing and feared dead after water poured into the underground shafts where they were digging.
Authorities said on Thursday that Wednesday's accident at El Tunel mine in the northwestern town of Riosucio was likely triggered by an explosion or power outage that disabled pumps used to extract water and supply oxygen to work crews as deep as 27 metres below ground.
Al Jazeera's Alessandro Rampietti, reporting from the scene, said: "Over 40 hours into the rescue operation the rescue teams have not Been able to reduce the level of the water.
"That's because the water from the river is filtering into the mine from underneath. The rescuers say it is very unlikely to find anyone alive."
Yeison Gutierrez, 34, said he was able to save several colleagues because he was one of the few miners who knew how to swim. But one co-worker slipped through his hands and didn't make it above ground.
"I swam to the surface fighting against the water and the air pressure, that's how we were saved," Gutierrez told the AP news agency from the mine where he was assisting rescuers.
President Juan Manuel Santos called on rescuers to "spare no effort" in the search.
Family members huddled near the mine through the night as crews used pumps to remove water that had raced into three vertical shafts from the adjacent Cauca river.
Authorities said it could take at least three days to clear the mine.
"Every hour, every minute and every second that goes by the chances of finding survivors diminishes," said Jaime Gallego, a civil defence worker.
Mining accidents are common in Colombia but usually take place in wildcat mines dominated by leftist rebels and criminal gangs.
Natalia Gutierrez, the head of the National Mining Agency, said the mine that collapsed Wednesday was in the process of being legalised.
But she told Caracol television that preliminary accounts from the site raised questions about whether the mine was complying with safety protocols.
The national ombudsman's office on Thursday called on authorities to investigate the mine's owners for negligence and reinforce controls at the estimated 3,000 other semi-illegal mining projects seeking government authorisation.
Gutierrez, the miner, said workers earn a percentage of the gold they extract, with wages ranging between $400 and $800 per month.
Source: Al Jazeera and agencies