BOGOTA (Reuters) - An explosion at a coal mine in Colombia's Boyaca province killed 11 people and left four missing, the national mining agency (ANM) said on Sunday.

       The accident occurred on Saturday night and was caused by a build up of methane gas at the mine, which is located in the Tasco municipality, the ANM said.

       Colombia's mining industry includes huge open-pit and underground projects operated by multinational companies, as well as hundreds of small, informal deposits.

       Accidents in the mining sector occur regularly as some enterprises are illegal, or do not properly enforce safety measures.

       The mine in Tasco had approval to operate, the ANM said. Rescue crews and fire fighters fear that the four people still missing were also killed in the explosion.

       Colombia saw 128 mining accidents in 2021, which killed 148 dead. So far this year 19 mining accidents have taken place, with 36 deaths, according to the ANM.

       (Reporting by Luis Jaime Acosta; Writing by Oliver Griffin; Editing by Michael Perry)