In short, US government yes, CIA maybe. In 1959 the US military sent a team to Colombia to assess its internal security situation. They were worried about communist insurgencies causing further problems in the country. In 1962, the US Special Warfare Center sent General William P. Yarborough to institute a comprehensive counterinsurgency strategy which became known as Plan Lazo. Part of the plan's mission was to build up civil society and a major component was the so called "civil defense committees". These were armed civilian organizations that worked alongside police and military personnel to combat groups like the FARC. So the US military was involved from the beginning with these groups for sure. I don't know of any CIA documents that specifically mentioned support for these groups so I won't speculate on what the CIA did or did not do.

Source: "Guerrillas, Bandits, and Independent Republics: US Counterinsurgency Efforts in Colombia 1959-1965" Small Insurgencies 6 no. 3, (1995) 304-327