Ataullah Khogyani, spokesman for the provincial governor in Nangarhar, said Saturday the number of ISIS terrorists dead was up from the 36 reported a day earlier.
A Ministry of Defense official had said Friday that the number of dead could rise as officials assessed the bomb site in Achin district.
The U.S. attack on a tunnel complex in remote eastern Nangarhar province near the Pakistan border killed at least four ISIS group leaders, Khogyani said. He said a clearance operation was continuing.
There had been heavy fighting in the area in recent weeks between Afghan forces and ISIS militants.