CHICAGO (CBS) — Chicago Police have declared the site of a fatal fire, a crime scene.

It happened this morning in the 4200 block of W. 21st St. in the city’s Lawndale neighborhood. The fire in a two-flat building sent six people to the hospital. Firefighters were called to just after 4:30 a.m. Saturday.

Four of the victims suffered severe burns and were all eventually transported to John H. Stroger, Jr. Hospital. Taniya Johnson, of the 4500 block of West Harrison Street, and Nathan Beller both died from the fire.

Johnson’s two children, identified by family as Nariya her 3-year-old daughter and Naciere her 9-year-old son, were criticality injured, officials said.

The girl, who authorities said is four-years-old, suffered burns to 100 percent of her body and her brother, who authorities say is 8, suffered burns to 35 percent of his, fire officials said. Both remained in critical condition Saturday evening at Stroger Hospital, a spokeswoman said.

“The last person they pulled out of that place, I’d say she was severely burned. Her hair was singed, her body, I could see the skin peeling off of her. It just didn’t look good at all. It was horrible,” said Ferdinand Miranda, a witness who saw the young girl being pulled out of the home.

Investigators are now trying to determine whether the fire was intentionally set.

“That’s under investigation right now and our O.F.I., Police, and Bomb and Arson are here investigating. At this point, the source of fire looks like it was in the bedroom,” said James Purl, 14th Battalion Chief.

Sources say the fire officials believe an accelerant was used.

Firefighters say the fire started in a front bedroom, on the first floor of the two-flat building, and spread to the living room. The bedroom is where firefighters found the mother and the two children were rescued from the living room.

The male victim was outside when fire crews arrived.

Two elderly women, who lived in the building’s second floor unit, also transported to hospitals and treated for smoke inhalation.

The Red Cross tells CBS 2, the two children did not live in the home, and were visiting.

A total of seven people from two different households, were displaced by the fire and will receive assistance.

The Sun-Times Media Wire contributed to this report.

Watch & Listen LIVE