The girl was inside her family’s house when the building collapsed and killed her, the province’s governor, Douglas Cagas, told CNN.
Fire Service director Chief Superintendent Samuel Tadeo confirmed the three deaths and also said a market in Padada had collapsed.
The country’s second-largest island is a popular tourist destination, and videos posted on social media showed hotel pools dramatically overflowing and mass evacuations of shoppers from malls.
Residents reported schools had been severely damaged — luckily empty of students at the time, as the quake happened on a Sunday. Governor Douglas Cagas of the island’s Davao del Sur province said a three-story building had also collapsed.
There were several aftershocks in nearby provinces, including a 5.0 magnitude, according to the US Geological Survey. It added that there was no tsunami threat, as the quake struck inland and not the water.
It’s the latest in a serious of quakes to strike the island in recent months. In October another series of 6.6 and 6.5-magnitude quakes struck Mindanao, killing 14 and injuring more than 400.