Former presidential candidate Ingrid Betancourt, abducted in 2002, said she and her fellow captives are "living like the dead."
Last week, Colombian officials confiscated from suspected rebels five videotapes of hostages, including images of three U.S. contractors, as well as images of Betancourt and the letter to her mother.
The three U.S. contractors were abducted by the Revolutionary Armed Forces of Colombia, or FARC, in 2003 when their plane crashed.
Betancourt was taken hostage by FARC the previous year. There has been little evidence of their survival since.
El Tiempo reported the dates of the videos were Jan. 1 and October of this year.
FARC, Colombia's largest rebel group, has been fighting government forces for more than 40 years.