Decomposed bodies of 16 miners kidnapped nearly a decade ago in Khyber Pakhtunkhwa have been found in a mass grave, officials said on Friday. 

The miners went missing in December 2011 in Khyber Pakhtunkhwa -- once a stronghold of the Taliban, who raised funds by kidnapping workers for ransom.

Rescue 1122 personnel had been searching Tor Chappar, a valley in Dara Adam Khel near Kohat City, some 50 kilometres southwest of Peshawar, for two months after getting new information on the case from relatives of those kidnapped.

"The medical teams have examined and confirmed that they are all sixteen," Khyber Pakhtunkhwa Information Minister Kamran Bangash told the media. "All... are decomposed and beyond recognition," he added.

Bilal Ahmad Faizi, a spokesman for the rescue service, confirmed the operation.

Earlier this year 10 miners were kidnapped and then murdered in an attack claimed by the Islamic State group in the restive southwestern Machh area.