Cotabato City Mayor Muslimin Sema said the two children and the other fatalities were thrown off when the 10-wheeler truck lost control while negotiating a curve along Quezon Avenue in Cotabato City.
The truck was transporting hundreds of sacks of corn, and picked up the passengers along the way, he added.
The driver was being questioned by police, Sema said.
Inspector Wally Kasuyo, Cotabato City police spokesman, said the victims died from fractures in the heads and different parts of the body after they fell on the concrete pavement and bags of corn, each weighing more than a hundred kilos, landed on them.
Driver Edwin Flores, 35, claimed to have lost control of the truck when the master brake cylinder malfunctioned while he was maneuvering a downhill curve at Sinsuat Avenue, he added.
Witnesses said the truck wiggled and repeatedly rolled over before crashing into the Central Bank building.
Kasuyo said the truck, owned by a Muslim trader in South Upi, Maguindanao, was on its way to the public market in Cotabato City to deliver some 20 tons of yellow corn.
The fatalities were all residents of Barangay Biarong, a hinterland district in South Upi, some 50 kilometers southwest of Cotabato City, he added.  With AP