OAKLAND, Calif. — Federal officials investigating a fire that killed 36 people during a party at an Oakland warehouse plan to bring in engineers to examine the building’s electrical system, as they try to pinpoint the cause of a blaze that has cast a spotlight on similar artists’ colonies around the country that offer cheap housing but unsafe living conditions.

Federal investigators said Wednesday the fire started on the ground floor of the Oakland warehouse and quickly raged, with smoke billowing into the second level and trapping victims whose only escape route was through the flames.

“The occupants were consumed by smoke before they could get out of the building,” said Jill Snyder, special agent in charge of the San Francisco office of the Bureau of Alcohol, Tobacco, Firearms and Explosives.

She also confirmed there were no sprinklers or fire alarm system in the building.

Officials previously said recovery efforts at the site had ended with the death toll remaining at 36.

Snyder reiterated that investigators were examining a refrigerator and other possibilities as a potential source of the fire but had not reached any conclusions. She said the electrical system would be examined. Investigators have not found evidence of arson, but she said they have also not ruled it out.

Snyder indicated it would be at least several weeks before the investigation was completed.

Officials hope to create a virtual, 3D reconstruction of the building for criminal and civil investigations and to provide answers to family members about their loved ones’ last moments, Alameda County sheriff’s Sgt. Ray Kelly said.