FORT COLLINS, Colo. (CBS4) – Investigators in Fort Collins say they have determined how a fire at an apartment complex got started.

Investigators with the Poudre Fire Authority say an improperly stored charcoal grill sparked the fire at the River Glenn Apartments.

The fire broke out early Saturday morning and more than two dozen people and their pets had to evacuate in frigid temperatures. All but 12 of them were able to return immediately.

One person suffered non-life threatening burns and was taken to a hospital.

River Glenn Apartments is located in the 1100 block of Davidson Drive.