An estimated 800 people were attending the funeral of Javed Iqbal in the town of Mingora in the Swat valley, when the bomb went off, security officials said.
Ghazan, Iqbal's 16-year-old son, was among the dead after the funeral bombing.
Police began searching for clues on Saturday.
Death toll rising
Arshad Majid, the district police chief, said 40 bodies were accounted for, but the toll was expected to rise after forensic officials reconstruct body parts.
Another suicide bombing on Saturday killed one person and wounded 19 people, mostly security personnel, in the region, officials said.
The bomber struck a vehicle carrying security forces in the northwestern tribal region of Bajur, according to Iqbal Khatak, a government official.
He said the severed head of the attacker, who was on foot, was found at the scene.
All the victims were taken to a hospital where three of them were in critical condition, he said.
Immediately after Friday's suicide bombing in Mingora, authorities made an emergency appeal for blood donations.
Syed Kamal Shah, health minister of the North West Frontier Province (NWFP), told the AFP news agency: "We are facing difficulty in the relief operation because the blast also damaged an electricity transformer in the area."
Major-General Nasser Janjua, a regional commanding officer, said earlier in the week that 400 fighters were hiding in the valley.
"Nobody has claimed the responsibility for the attack, but we suspect the involvement of miscreants (militants) against whom the military operation was being carried out," another senior security official said.
Pakistani forces have been searching for Maulana Fazlullah, a religious leader who called for Islamic law in the valley.
The army launched a major offensive in November to drive his followers out of Swat.
Last year, about 2,000 people were killed in violence across Pakistan.