U.S. espionage operations targeting top Colombian government officials in 1993 provided key evidence linking the U.S.-Colombia task force charged with tracking down fugitive drug lord Pablo Escobar to one of Colombia’s most notorious paramilitary chiefs, according to a new collection of declassified documents published today by the National Security Archive. The affair sparked a special CIA investigation into whether U.S. intelligence was shared with Colombian terrorists and narcotraffickers every bit as dangerous as Escobar himself.

The new documents, released under the U.S. Freedom of Information Act, are the most definitive declassified evidence to date linking the U.S. to a Colombian paramilitary group and are the subject of an investigation published today in Colombia’s Semana magazine.