A mother and her daughter died after a large fire tore through a two-story apartment building in Downey Tuesday night.  

The fire was reported near the intersection of Tweedy Lane and Dinsdale Street around 10:45 p.m., according to the Downey Fire Department.

Aerial video from Sky5 showed heavy flames and smoke billowing from both sides of the structure as firefighters were still arriving on the scene.  

Crews could be seen battling flames on the side of the building in an attempt to keep the fire from jumping an alley to another structure.  

One victim, a woman, was found outside the building with burn significant injuries, Fire Department Battalion Chief Jorge Villanueva said. She suffered first and second-degree burns on about 20 percent of her body, officials say. She was taken to a local hospital.

Crews learned there were two additional victims still inside the structure and began search efforts.

“They encountered high heat and low visibility and extreme fire conditions,” Villanueva said.

The victims, described as a single mother and daughter, were found trapped in an upstairs bathroom and brought down in cardiac arrest, Villanueva said.

The mother, who has not been identified, was pronounced dead at the scene.

The daughter, believed to be about 12 years old, was resuscitated and transported to a local hospital, where she later died, officials said.

Neighbors explain the units are two stories with garages, living rooms and kitchens on the ground floor and bedrooms on the second floor.

Friends tell KTLA the victim was living with her four children in one unit — two boys with autism and two girls.

The woman’s mother, the grandmother, lived next door. Those close to the family say the fire apparently started in the grandmother’s garage.

The initial burn victim is believed to be the grandmother of the 12-year-old, and she was taken to Los Angeles County + USC Medical Center for treatment. She remains in critical condition.

Fire crews say the smoke detectors were working and sounding off when firefighters arrived.

Authorities say the victim’s three other children remained unharmed and are with family.

The cause of the fire remains under investigation.

Anytime there’s a fatality or any sort of traumatic injuries to the citizens that we serve, it hits us all pretty hard,” authorities said.

Emergency crews say everyone should have an exit plan in the event a fire ignites inside their home. Officials advise conducting safety drills with your family and ensuring smoke detectors are always fully operating.