The landslide struck Tuesday night in a mining village in Davao de Oro province on Mindanao island, trapping at least 20 people inside two buses used to transport mine workers, provincial disaster official Edward Macapili told AFP.
At least 28 people were on board the buses when the landslide hit, but eight managed to escape unhurt through the windows before the mud engulfed them, Macapili said.
The buses had been outside a gold mine operated by the Philippine company Apex Mining in Masara village where buses drop off and pick up workers.
Five bodies were pulled from the mud, Macapili said, but it was not clear if they were on the bus.
Another 31 villagers were also injured. Two of them were seriously hurt and were airlifted to a hospital in Davao city for treatment, Macapili said.
"There was no sign that a landslide would occur because the rains stopped on Thursday and by Friday it was already sunny and hot," Macapili said.
Macapili said an earthquake shook the village shortly after the landslide. The search effort was halted at midnight because it was too hazardous to continue, but resumed at daylight, he said.
"Rescue work is hampered by limited visibility and intermittent slides," Apex Mining said in a statement on its website.
It is not clear if other mine workers were also affected by the landslide or if other villagers are missing.
Meanwhile, 285 families from Masara and four nearby villages were forced to evacuate from their homes, Macapili said.
Military personnel have been deployed to help in the rescue efforts.
"The roads remain impassable, and there is no cellphone signal in the area," the military's Eastern Mindanao Command said on Facebook Wednesday.
Rain has pounded parts of Mindanao off and on for weeks, forcing tens of thousands into emergency shelters.
At least 18 people died from landslides and flooding in the region last week, the national disaster agency said in its latest update.
Landslides are frequent hazards across much of the archipelago nation owing to the mountainous terrain, heavy rainfall and widespread deforestation.
The Philippines is regularly ravaged by storms, with scientists warning they are becoming more powerful as the world gets warmer because of climate change.