An explosion at a coal mine in central Colombia has left 21 miners dead after 10 more bodies were found in the pit, President Gustavo Petro said on Thursday.

"Sadly, 21 people lost their lives in this tragic accident in Sutatausa," a municipality in Cundinamarca department, the Colombian leader wrote on Twitter.

A build-up of methane gas apparently triggered the Tuesday night explosion in the underground complex, according to local officials.

Rescuers had found 11 other bodies on Wednesday in the mine, which is some 45 miles (75 kilometers) north of Bogota.

Cundinamarca Governor Nicolas Garcia announced the search was over on Thursday, writing on Twitter that "unfortunately there is no longer anyone alive. We are heartbroken."

Dozens of rescuers had searched for the miners in six interconnected legal mines, where officials are now investigating whether there was appropriate air flow.

Sutatausa's mayor, Jaime Arevalo, had earlier described the rescue effort as "very complex," saying oxygen was running out and water was "beginning to accumulate."

"I felt like I was going to drown and you couldn't see anything," Joselito Rodriguez, a miner who escaped after the explosion, told AFP.

Family members shared photos of the victims -- mostly young men -- on social media.

In order for methane not to explode, proper ventilation and monitoring systems allowing for alerts and split-second decision making are needed, Javier Pava, director of the National Unit for Disaster Risk Management, told outlet Canal Institucional.

"It will have to be reviewed if these existed or not," he said.

'Not acceptable'

Oil and coal are the main exports of Colombia, where mining accidents are frequent, especially at illegal digs in Cundinamarca and other departments in the country's center and northeast.

Colombia registered more than 1,260 mining accidents from 2011 to May 2022, for an average annual toll of 103 deaths, according to official data.

At least 130,000 people make a legal living from mining in Colombia.

Pava said there have been 23 miner deaths recorded this year.

"This is not acceptable: that we have so many people losing their lives in an activity such as this, which is very dangerous but that needs not just regulations but substantive decisions," said Pava.

Unions consistently denounce poor working conditions, with a lack of protective gear and long working hours.

In August, nine miners were rescued from a collapsed illegal coal mine in the same department.

And last June, 15 people died at a mine near the border with Venezuela, also due to a gas explosion.

According to the ministry of mines and energy, in 2020 Colombia had 53 percent of proven coal reserves in Latin America and 0.6 percent of worldwide reserves.

Petro, who became president in August, has referred to coal as "poison" and vowed to transfer mining jobs to the agriculture, clean energy and tourism sectors.

Illegal mining, along with drug trafficking, is also a major source of income for Colombia's armed groups that have waged a nearly six-decade conflict among each other and against security forces.