Colombia, the world's No. 5 coal exporter, has seen a drop in violence after a U.S.-backed crackdown on rebels, and foreign investment has risen sharply.
But attacks are still a risk in rural areas where state presence is weak.
A blast hit the coal railway operated by Cerrejon, the country's largest coal producer, in a remote northern region of country, the company and police said.
A spokeswoman for Cerrejon said damage was very limited and exports were unaffected by the attack.
Cerrejon, operated by BHP Billiton , Anglo American and Xstrata , produces on average 85,000 tonnes a day of high-quality thermal coal.
Violence, kidnapping and bombings from Colombia's long war have ebbed since 2002 when former President Alvaro Uribe began a hard-line campaign against FARC rebels and negotiated the disarmament of outlawed paramilitary militias.
Companies are still targeted by illegal armed groups for extortion and occasional kidnapping attempts.
Fueled by the cocaine trade, Colombia's conflict still impacts rural areas, where former paramilitaries, leftist rebels and criminal gangs often fight or form loose alliances over drug trafficking routes. (Reuters)
