Locals were warned to evacuate the area in the municipality of Bello, which remained vulnerable to landslides, the governor of the Antioquia department Andres Julian Rendon said while confirming the casualties.
At least 15 people were still missing after the tragedy, which was caused by flooding in a ravine, according to media reports, AFP reported.
Images shared by local media showed houses buried under earth on a mountain bordering Colombia's second-biggest city.
A picture shared by Medellin's disaster management department showed a car and a street caked in mud.
Other X users shared images and videos of flooded Bello streets.
Antioquia, which is situated in the western Colombian Andes, is often affected by landslides during the rainy season.
At least five people were killed in a landslide in another Medellin suburb, Sabaneta, last month.