Six people were taken to the hospital following an apartment fire early Sunday morning in the Kenwood neighborhood.

It happened around 4 a.m. in the 1200 block of East 46th Street.

Fire officials said it started in the rear of the three-story building and has since been contained.

Six people were taken to the hospital—five in critical condition and one in serious condition. 

According to a source, a teen jumped from the window to escape the fire, and three others suffered cardiac arrest. The ages of the other victims were not released. 

One witness at the scene described what she saw.

"I heard the lady walking. She said it just got out of control, and then the neighbor say that a couple of people had to jump. So. I don't know if they're hurt. I'm pretty sure they're hurt," Elaine Mason said. 

The cause of the fire remains under investigation.

This is a developing story. Check back for updates.