According to data released by Colombia's Search Unit for Missing Persons, known by its Spanish acronym UBPD, at least 137,000 people have been reported missing in connection with the country's armed conflict since 1921. Photo by Mario Caicedo/EPA

Aug. 31 (UPI) -- When Tobías Borda Cepeda disappeared in rural Colombia in 1921 amid local land disputes, his family could not have foreseen that his case would mark the beginning of a tragedy that would span a century.

According to data released by Colombia's Search Unit for Missing Persons, known by its Spanish acronym UBPD, at least 137,000 people have been reported missing in connection with the country's armed conflict since that year.

Marking the International Day of the Victims of Enforced Disappearances on Sunday, the agency said 48.5% of all cases occurred during the 2000s, with the highest concentration between 2001 and 2003.

Disappearances during the first decade of the 21st century represent a dark chapter in Colombia's recent history. Between 2000 and 2010, the country experienced an escalation in violence marked by fighting among right-wing paramilitary groups, left-wing guerrillas and state forces in a war waged on multiple fronts.