CHICAGO (CBS) — A two-alarm fire damaged two buildings Saturday morning in the South Side Washington Park neighborhood, leaving three families homeless.

The fire was first reported at 6:45 a.m. at a building in the 5800 block of South Prairie, according to Chicago Fire Department Cmdr. Walter Schroeder. It was upgraded to a two-alarm at 7:01 a.m.

The fire caused extensive damage to one building and also spread to an adjacent building, Schroeder said. No one was hurt.

It took more than four hours for crews to completely extinguish the fire. The cause has not yet been determined, but the Chicago Police Bomb and Arson Unit is assisting the fire department with the investigation.

Officials think the fire started in a vacant building and then spread next door, where five adults and three families were displaced from their homes, according to Red Cross spokeswoman Carolyn Moretti.

According to Mimi Simon, spokeswoman for the city’s Department of Buildings, it wasn’t the first fire to erupt at the vacant building this summer. It also went up in flames in late August, and is now most likely slated to be demolished.

Simon said that after the second fire, “the damage is extensive and we are bidding it out as a demolition.”

City inspectors routinely check properties after a fire to determine if it can be saved.  Simon said that after inspection, “It appears that we are moving forward with an emergency demolition.”

The Red Cross and the Illinois Department of Human Services were on the scene this morning, supplying food and shelter to the displaced residents.

The Red Cross will provide the individuals and families with ongoing shelter “until they are able to move somewhere else or back into their homes,” Moretti said.