Alameda County sheriff's officials said they anticipate the number of victims to rise. The youngest victim was 17 with most of the others believed to be 20-30 years old. Several were international students and officials are reaching out overseas to contact their families.
They called it the city's worst fire in recent memory.
The Alameda County District Attorney's Office has also launched a criminal investigation into the fire, officials announced Sunday.
Oakland officials said eight victims have been positively identified as having died in the fire.
They released names of seven victims:
-- Cash Askew, 22, of Oakland.
-- David Cline, 24, of Oakland.
-- Nick Gomez-Hall, 25, of Coronado.
-- Sara Hoda, 30, of Walnut Creek.
-- Travis Hough, 35, of Oakland.
-- Donna Kellogg, 32, of Oakland.
-- Brandon Chase Wittenauer, 32, of Hayward.
The eighth victim was a 17-year-old minor whose name will not be released, officials said.
Officials said the death toll may rise as they still don't know exactly how many people were inside the warehouse prior to the fire.
"We're expecting the worst and hoping for the best in regards to how many victims we'll find," said Alameda County sheriff's Sgt. Ray Kelly.
An electronic music party late Friday night, with what officials believe had up to 100 people, was being held inside the converted warehouse, known as the "Ghost Ship" when a fire tore through the building Friday night.
KGO-TV spoke to an official briefed on the situation, who said early indications show that the blaze was not arson but appears to be an electrical fire. Those details were not yet confirmed.
The building did not have fire alarms or sprinklers or proper exits. The only exit from the second floor, where the event was being held, was a makeshift staircase of wooden pallets. Officials said once the fire started, people became disoriented inside, which made it difficult to escape the flames.
Coroner officials were asking loved ones of the missing to preserve sources of DNA on toothbrushes or hairbrushes by placing them into a clean paper bag.
Recovery crews worked through the night to remove debris and get to victims, who many were found in small groups trying to exit the building.
The number of victims was really taking a toll on crews.
"It is tragic to watch so many people perish from a fire fatality in front of your eyes and have to be stoic in your job, be professional in your actions, and make sure that we are honoring the victims and their families to bring them safely out of the building," said Oakland FD Batt. Chief Melinda Drayton, holding back tears.
Dump trucks were being used to haul stuff out so investigators can get in and continue their search for more victims, making it a painful waiting period for families and friends of the partygoers who are still missing.
MORE: SoCal women fear friends did not survive Oakland warehouse fire
Families and loved ones were advised to head to a sheriff's substation on East 12th Street for updates.
The Ghost Ship warehouse is a large building where artists gathered to do their work and share ideas.
Some have said there were people living there, and those who have been inside describe it as a place where individual living spaces were sectioned off with partitions.
City officials confirmed the building was not permitted for residential use. The building's owner also had received several code violations in recent weeks, but it was not yet clear whether he would be facing any criminal charges.
MORE: Oakland Ghost Ship warehouse founder disregarded fire hazard warnings, ex-employees say
Oakland Mayor Libby Schaaf said 14 people who lived in the Ghost Ship got out and were taken to the hospital, but dozens of families still don't know if their loved ones are alive or dead.
"She's not answering her phone. She's not answering her phone. No one can get in contact with them. I tried calling. It's not like her not to respond to a text," said Kim Gregory, mother of a missing person.
Dan Vega said he is looking for his brother, Alex Vega, and Alex's girlfriend, Michela Gregory. They've been together four years and work together at a mortuary in Daly City. Michela's car was found near the scene of the fire.
"I think I'm just more infuriated that I'm not able to help. I want to be there," said Dan Vega, frustrated. "Give me some gloves. I got work shoes. I'm ready. Let me find my brother."