Michigan City, Ind. ? A fire killed four people early Sunday in a two-story house where about a dozen people lived in makeshift rooms, some of them bedding down in closets, the state fire marshal said.

Witnesses saw people fleeing the property before officials arrived, Fire Marshal Roger Johnson said. The residents didn’t return, he said.

“We don’t know why they left, why they did not want to stay and why they did not want to address any questions we may have,” Johnson said.

Immigration officials had been to the scene, Deputy Fire Chief Chuck Greis said. Neighbors said they believed most residents in house were Asian immigrants who worked at a local Chinese restaurant.

The fire appeared to have started in the back of the house, but investigators did not yet know the cause, Johnson said. An accelerant-sniffing dog was being used and a task force was formed to investigate, including agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives.

When fire crews arrived, the rear of the home was fully engulfed in flames and within minutes the fire had spread through the entire house, Fire Chief Ralph Martin said. He said the fire appeared to have traveled through the walls or ceilings. Crews needed three hours to extinguish the blaze.

Michigan City firefighters bring out an accelerant

Johnson said he did not know how many people were there when the fire started but he said there were “an abnormal number of sleeping areas in the house.” Mattresses were found inside closets and there appeared to be some makeshift rooms with spots for about 12 to 15 people to sleep, he said.

Neighbor Holly Hanrath said the house had been up for sale and she and her husband Frank had been inside about two weeks ago. She said it had been subdivided into rooms with plywood sheeting and there were mattresses on the kitchen floor. The couple said the wiring and plumbing were old and they could smell gas near the stove.

The Hanraths live across the street. “I could feel the heat coming in through my window. It was really intense,” Frank Hanrath said.

Officials did not know the victims’ identities or ages.

Michigan City is in northwestern Indiana, about 35 miles east of Chicago.