According to a Dow Jones Newswires report citing government officials from Bogota, coal output was 18.4 million tons, a 21.4% reduction over the same period in 2012.
Recent strife in the Andean nation has already resulted in an adjustment of whole-year numbers.
In April, government statistics agency Departamento Administrativo Nacional de Estadística said the industry would target 94Mt this year, down from a previous 97Mt.
Among the obstacles were a month-long labor strike at the Cerrejon complex – a top producing operation jointly owned by Glencore Xstrata, Anglo American and BHP – and a temporary suspension of Drummond’s port load-out operations after the producer allegedly dumped coal into the water following a vessel accident.
Government officials recently said Colombia’s economic growth in 2012 was 4%, down from 6.6% in 2011.
This year, DANE is forecasting economic growth of 4.8%, while the country’s Central Bank has estimated an expansion of 4.3%.
Production figures have taken a downward turn over the last few years.
President Juan Manuel Santos, who came into his seat in 2010, initially estimated 2013 output of 100Mt and 114Mt next year.
Colombia is the world's fourth-largest coal exporter.