The country’s national mining ​agency had weeks earlier warned that a buildup of gases at the mine could become dangerous.

A coal mine explosion in Colombia’s Cundinamarca province killed nine workers and injured six, the National Mining Agency said, weeks after issuing risk-control recommendations for the site.

The blast on Monday at a legally operated mine in the Sutatausa municipality, 72km (45 miles) north of the capital Bogota, was caused by a buildup of gases, the agency said.

Colombia is home to numerous open and underground gold and coal mines. Explosions and other incidents frequently occur, mostly at operations that are illegal or do not adopt sufficient safety measures.

The blast occurred at a mine operated by the company Carbonera Los Pinos, where the miners were working at least 600 metres (2,000ft) underground, local authorities said. The company could not immediately be reached for comment.

Cundinamarca Governor Jorge Emilio Rey said on X that the explosion was “apparently due to a buildup of gases”.

The governor had previously said 12 people were trapped and three had managed to escape.

Rescue workers were on their way to the site, he said, sharing images of ambulances at the mine’s entrance.

Authorities were assessing gas levels in the mine before conducting rescue operations, he added.

The injured were taken to a local hospital for treatment.

“We deeply regret this tragedy and send a message of condolence, solidarity, and support to their families,” said Rey.

The mining agency had recommended that the mine strengthen its safety measures during a site visit on April 9, in which ⁠it had identified gases, including ⁠methane, that it said could become dangerous.

“As the ANM has warned during its inspection visits, coal deposits can present accumulations ⁠of gases such as methane, as well as concentrations of coal ⁠dust,” the agency said in ⁠a statement.

“The National Mining Agency expresses its solidarity with the families of the victims and regrets this mining accident in which, thanks to timely rescue efforts, six miners were rescued alive.”

Mining accidents in Colombia usually occur due to poor ventilation.

In the area where Monday’s incident took place, illegal mines that fail to meet safety standards are also in operation.