Up to 100 rescue workers have continued to search for sixteen people trapped underground after an unlicensed gold mine was flooded in western Colombia, authorities have said.

Officials said the flooding on Wednesday was likely triggered by a power outage or an explosion deep underground in the mine located in northwestern Colombia.

The accident happened on an indigenous reservation in the municipality of Riosucio.

Al Jazeera's Alessandro Rampietti, reporting from Colombia, said that "it is clear the four deep tunnels were inundated by an issue with the motor-pumps that drain the mine."

"The mine's owners say the electrical company cut off the power, while the company says the mine was illegally attached to the electrical system and the system failed due to a short-circuit."

Some of the miners are trapped at a depth of about 17m, others at about 10m, said the police commander for the department of Caldas, Luis Duarte.

Colombian President Juan Manuel Santos called on rescuers to "spare no effort" in the search.

An owner of the mine fears that the 16 miners are all dead. He said it will take at least three days for rescuers to pump out excess water from an adjacent river that flooded the shafts when the accident took place.

Fatal mining accidents are common in Colombia and caused the death of 120 people last year. That is the highest tally since 2011.

Business has boomed over the past decade for Colombia's illegal miners as the price of gold has risen from less than $400 per ounce to almost $1,200.

Colombia is a major gold producer, with output of more than 55,000kg in 2013, according to government figures.

Last week, Colombian authorities arrested nearly 60 people in raids targeting illegal mining operations used to finance the Revolutionary Armed Forces of Colombia (FARC), the leftist armed group that has waged a
five-decade war on the government.

The areas targeted were in the south and east of the country.

Mining revenues represented 2.3 percent of Colombia's national income in 2012, but more than half its mines are unregulated, according to official figures.

Source: Agencies