Mintu Mia, who was in Tangail District Jail in drug case, escaped from Sir Salimullah Medical College, also known as Mitford Hospital, on Saturday morning.
The 28-year-old was admitted to the hospital on August 28 evening with symptoms of respiratory distress (chronic obstructive pulmonary disease) and chest pain, said Brig Gen Kazi Rashid-un-Nabi, director of the hospital.
"The prisoner was guarded by jail police. So, it is their fault," he added.
Kamrul Islam and prison guard Abdul Alim were on duty from 10pm to 6am. However, the prisoner escaped at 3:40am.
Earlier on August 12, Mintu was admitted to Dhaka Medical College and Hospital but was taken back to the jail on August 13 after recovery.
