The incident came to light after neighbours in the small town of Darya Khan - some 300 kilometres from here - in Bhakkar district complained of foul smell.
When the police raided the house today, they found the head of a 2 to 3-year-old boy.
Mohammad Arif, who was arrested from the spot - less than a year after he was freed from jail following conviction on similar charges, said the body was stolen by his brother from a graveyard.
Terrorism charges have been slapped against them, Express Tribune reported today.
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Ameer Abdullah Khan, Darya Khan Superintendent of Police, was quoted by BBC as saying, "We found the severed head of a young child, about two or three years old."
"They probably dug up his body from a grave, but the identity of the child and the graveyard from where his body might have been stolen is not clear.
"During initial interrogation, Arif has admitted the body was chopped and cooked, but blames it all on his elder brother and denies he either helped him or devoured the curry," Khan said.
They had reportedly dug up and devoured from up to 150 bodies before they were finally caught.
Search operations are being conducted to arrest Farman.
Since Pakistan has no specific laws against cannibalism, they were first arrested under the Maintenance of Public Order (MPO) section of the Pakistan Penal Code (PPC) in 2011, and were later charged under section 295-A.
The duo was sentenced to two years' imprisonment and fined Rs 50,000 each.
After the completion of their sentence, they were released from Mianwali's district jail and returned to their hometown, much to the shock and dismay of locals.