Police said the landslide occurred before 6 a.m. in Agoncillo town, Xinhua news agency reported.
Agoncillo town Mayor Cinderella Reyes told a radio interview that the deaths include a 28-year-old pregnant woman, her nine-year-old child, and her siblings aged 13 and 15.
Reyes said rescuers recovered the bodies of the four. There are no reported missing so far, she added. Reyes said the town continues to evacuate villagers despite incessant rains and floodwater.
Gaemi, the third typhoon to batter the Philippines this year, is expected to leave the country by Wednesday night or early Thursday.
However, the state weather bureau warned that the rain would continue even after Gaemi leaves.