Colombia Reports said the research center Nuevo Arco Iris and Semana magazine reported Jaime Uribe had been arrested and interrogated by the army in 1986 after investigators discovered calls had been made from his phone number to Escobar.
The research center and the magazine reports come as Jaime Uribe's former partner and their daughter are to be extradited to the United States to face drug-trafficking and money-laundering charges.
Alvaro Uribe, Colombia's president from 2002 to 2010, said on Twitter his brother had been detained by the army over the alleged communication with Escobarl, but said his brother's "car phone was cloned by criminals" and his brother "was released after proving the cloning and the impossibility the made calls were his because of his health and hospitalization."
Jaime Uribe died in 2001 of throat cancer.
Alvaro Uribe said the two suspects to be extradited were the former partner and daughter of his late brother but not part of his family.
"My brother Jaime died in 2001, married to Astrid Velez, they had two children -- one professional in environmental [matters] and one girl who was born with cerebral palsy. Other romantic relations my brother might have had would have been private and unknown to me," the former president said.
Colombia Reports said 1991 U.S. military intelligence files said the ex-president was a "close friend" of Escobar.
Couple mistakenly served bag of cash at McDonald's drive-thru
Jordana Brewster on Paul Walker: 'He was an enormous presence in my life'