WASHINGTON (WUSA9) — Twelve residents are without a home after a blaze erupted on the roof of a three-story apartment building Tuesday afternoon.

D.C. Fire and EMS responded to the 1300 block of 12th Street NW for a two-alarm fire.

It was first spotted by an ambulance, a spokesperson said. Firefighters encountered heavy fire on the roof and began to fight it from inside but were forced out. They then used the tower ladder to knock down the fire, officials said.

There was at one point an explosion from a propane tank on the roof of the building. Officials are unsure at this time if that was the cause of the fire.

The fire did spread to the adjacent building, displacing an unknown number of people. A dog was badly burned and taken to City Paws Animal Hospital on 14th Street NW.

Three firefighters were transported to area hospitals, one with a sprained ankle and two others with heat-related injuries.

This is a developing story and will continue to be updated.