OAKLAND (KRON) — Oakland Fire and the federal Burea of Alcohol Tobacco and Firearms have concluded their on-scene investigation into the deadly Oakland warehouse fire that killed 36 people.

The three-alarm fire at the “Ghost Ship,” a warehouse at 1305 31st Ave. used as a live/work space by an artist collective, sparked last Friday at about 11:30 p.m. during an electronic music show.

At this time, the cause and the origin of the fire are still unknown, ATF officials said.

The electrical system is part of the ongoing analysis but no final determination has been made.

All of the scene information has been gathered. An analysis of the information will continue.

The Oakland Fire Department will prepare the final report fo the scene investigation, which will then be handed over to the District Attorney’s Office to support their ongoing criminal investigation.

Complaints mounted about the cluttered warehouse converted into an illegal artists’ colony before a deadly blaze ripped through earlier this month, but few — if any — made it to the Oakland Fire Department.

Oakland Fire Chief Teresa Deloach Reed said Tuesday there are no city records showing her department receiving concerns about the building , which former residents, neighbors and others say was the subject of numerous calls to 911.

“We do not inspect buildings, we inspect businesses,” Reed said during a press conference. “There were no indications this was an active business.”

City administrator Sabrina Landreth, who also is in temporary charge of the Oakland Police Department, said officials are compiling and reviewing police records to determine how many times officers responded to complaints about the warehouse.

The deadliest structure fire in the U.S. in more than a decade broke out during a Dec. 2 late-night dance party in the cluttered warehouse. It killed 36 people. The building had been converted to art studios and illegal living spaces, and former denizens said it was a death trap of piled wood, furniture, snaking electrical cords and only two exits.

Prosecutors have warned murder charges are possible as they determine whether crimes are linked to the blaze.

Alameda County District Attorney Nancy O’Malley said Tuesday the criminal investigation will be “thorough, methodical and calculated.”

City and state officials fielded complaints for years about dangerous conditions, drugs, neglected children, trash, thefts and squabbles at the warehouse, raising questions about why it wasn’t shut down.

There are no records that inspectors from the fire and building departments ever set foot in the warehouse.

The fire chief said the warehouse wasn’t on the department’s list of businesses to inspect because no one ever applied for permits to occupy the building.Stay with KRON4 News for updates