Updated

A 14-year-old girl is dead and her mother and three siblings are in critical condition following a Sunday morning apartment fire in west Phoenix.

Firefighters responded at 12:45 a.m. to a report of a blaze in a second floor unit of an apartment building, fire department Capt. Jonathan Jacobs said. They battled heavy smoke to quickly put out the fire and found the victims.

Phoenix police Officer James Holmes said a firefighter kicked open a bedroom door and found the family.

"What he found was five family members -- a 33-year-old mother and her four children -- inside of that bedroom. All of them were unconscious," Holmes told The Associated Press.

Holmes said the mother and a 10-year-old are hospitalized in critical condition, and a 3-year-old and a 3-month old are extremely critical but stable.

The fire may have been intentionally set, and could be related to a case of domestic violence, Holmes said. A person of interest has been detained, he said.

Nearly 30 other people who live in the building were displaced because of electrical damage and other problems.

Among them is Jennifer Sheppard, who lives with her four children in a two-bedroom unit below the victims, who lived on the second floor. Sheppard said she is thankful a neighbor knocked on her door, waking up her 14-year-old son.

"I didn't hear anything. I didn't feel anything," Sheppard said.

Sheppard and her kids ran outside barefoot and that's when they saw the magnitude of the fire.

"It just hit me, all that heat toward my face," Sheppard said.

They then watched firefighters carrying the children over their shoulders and place them on the ground to administer CPR.

Sheppard said she didn't know the family well and never saw any domestic violence between the mother and her live-in boyfriend. The kids were usually playing on the balcony if they went outside, she said.

Sheppard said she still can't imagine what the mother must be going through.

"At least we got out safe," Sheppard said.

Hayla Miller, 12, who lives in another part of the complex and was close friends with the 14-year-old, said her friend was nice to everyone and fun to be around.

"She always made me laugh and I made her laugh," Miller said.