Sanchez said the group's findings also indicate that the government is readying to free about 40 more jailed dissidents.
"We are receiving information from the prisons that they are interviewing them, preparing them and asking what they plan to do when they get out," he said.
The Cuban government has been under increased pressure to free political prisoners, from both domestic and international quarters.
The Catholic Church entered into dialogue with the government in recent months to try to secure the release of some of the ailing political prisoners, and the Chilean president, Sebastian Pinera, has said his administration would also approach Cuba.
Miguel Angel Moratinos, the Spanish foreign minister, arrived in Havana, the Cuban capital, on Monday to support the church's efforts and attempt to save the life of a Cuban hunger-striker.
Cuban media reported earlier in the weekthat Guillermo Farinas, who has been on a voluntary fast for more than 130 days to demand the release of seriously ill political prisoners, is in danger of dying.
Although Raul Castro, Cuba's president, has labelled Farinas a common criminal and said the government would not yield to "blackmail", Spain's foreign minister hopes to secure the release of the 26 political prisoners in poor health, thereby meeting Farinas' demand and allowing him to end his hunger strike.