Islam was rescued from Salkosa at the trijunction of Kokrajhar, Bongaigaon and Dhubri districts in lower Assam late last night, the police said.
Islam was admitted to a local hospital in Bongaigaon. His health had deteriorated during his days in captivity, the police said.
Islam and his colleague Gadapani Pathak, engineers in agriculture engineering department and based at Gauripur in Dhubri district, were kidnapped on May 2 by four unidentified armed men at Kakragaon while they were returning to Guwahati from Dhubri in a car.
Pathak, a superintendant engineer, was shot dead by the kidnappers. His body was recovered a day later from Baitamari in Abhayapuri.
