Firefighters battled for hours to extinguish the blaze that started on Saturday morning on the third floor and spread to the floor above, trapping employees of a call centre.
Their chances of survival were “zero”, a local official was quoted as saying.
President Rodrigo Duterte met the families of the missing at the scene.
The cause of the fire was not immediately known.
Davao lies about 800km (500 miles) south-east of the capital Manila. (Courtesy BBC)