Firefighters work on the scene following a deadly fire at a warehouse in Oakland's Fruitvale neighborhood. (Elijah Nouvelage/Getty Images)

OAKLAND (CBS SF) — The official death toll in the Oakland Ghost Ship Warehouse fire grew to 33 mid-day Sunday after firefighters spent the night meticulously searching the burned-out wreckage of the dilapidated two-story building that served as an illegal music venue.

Officials asked families of those feared dead to preserve any DNA evidence they may have, including hair or tooth brushes.

At a 3 p.m. news conference Sunday, officials said firefighters were able to open access to the building and had searched 40 percent of the structure for victims.

CONTINUING COVERAGE: Deadly Oakland Warehouse Fire

“It was quiet, it was heartbreaking,” Oakland Fire Dept. battalion chief Melinda Drayton said of the search.

She said debris was being removed bucket-by-bucket from the burned out remains of the building with the search of 20 percent taking 12 hours.

Drayton said 10 of the new victims were discovered near the center of the building where the roof had collapsed.

Of those victims recovered, seven had been identified with three families notified overnight, Kelly said.

“This is very hard work and it’s very slow,” Sgt. Kelly said of the recovery process. Kelly said he expected the number of victims to rise.

Kelly said one of the victims was as young as 17, but they believed most of the victims were in their 20’s or 30’s. He also said some of the victims were from Europe, and Asia, and that they were working with the state department to notify embassies in those countries.

Sheriff’s officials have spoken to most of the family members of the victims, according to Kelly.

One of the victims was the son of an Alameda County Sheriff’s Deputy.

The death toll from the Oakland fire is the worst concert related disaster in the United States since the February 2003 blaze at the Station nightclub in Warwick, Rhode Island. That blaze erupted when pyrotechnics ignited flammable foam inside the club during a concert by the band Great White. In all, 100 people were killed and more than 200 were injured.

Oakland Mayor Libby Schaaf reportedly told families gathered at a nearby support center late Saturday night that all 14 known residents living in the building had escaped the flames.

While the cause of the Oakland fire had yet to be determined, and may not be determined for some time, it did erupt during the West Coast tour for the record label 100 Percent Silk.

It featured several DJs including two among the missing – Cherushii who is also known as Chelsea Faith and Oakland-based Nacht also known as Johnny Igaz.

At the fire scene, workers were forced to cut several new entryways into the building to allow searchers across to the artist collective that consisted of a maze of small work spaces on the first floor.

A makeshift stairway that one survivor likened to a plank served as access to the second floor where the concert/party was going on.

Survivors said what made it more difficult to escape was the cluttered interior of the building. The walls were covered with wood pieces of art and online photos of the cooperative display old furnishings scattered all about.

Laura Hobbs attended the party with friends and told of the panic and difficulties of those attempting to escape the deadly flames.

“The building itself was an art piece,” she said. “The walls were completely covered with makeshift pieces of wood, so finding the staircase if you’d never been there before was difficult because they had built it into the wall in a certain way.”

Schaaf and city building officials said the building had been licensed as a warehouse and not for residences or as a concert venue.

Darin Ranelletti, of the City of Oakland Planning Department, said the city had received reports of people living illegally in the building.

Officials had opened an investigation on Nov. 13. An investigator went to the premises on Nov. 17 but could not gain access to the inside of the building.

“We know last designated use for this building was a warehouse,” he said. “We received complaints about blight and unapproved construction … There was an inspection of the property and we were able to confirm blight we’re still investigating allegations of unapproved construction.”

The building was reportedly owned by Chor N. Ng of Oakland. Property records show he bought the warehouse in 1997.

Ng has not commented since the fire and may soon be the subject of a criminal investigation.

Mayor Libby Schaaf sais during Sunday’s 3 p.m. news conference that district attorney Nancy O’Malley activated the criminal investigation team, but noted that it was far too early to speculate as to the cause of the fire.

Officials also want to talk with Derick Ion, who heads up the artist collective.

Meanwhile, family and friends maintained an emotional vigil until late Sunday night at family support center.

They were awaiting a word, any word, of those who were believed to be missing. When it became apparent no further word of the fate of their loved ones would be coming they left the facility late Saturday night.

Condolences have cascaded down upon the victims from around the country, state and Bay Area.

Former Oakland Mayor and current California Governor Jerry Brown said he and his wife “were saddened to learn of last night’s tragic fire in Oakland. Our thoughts are with the entire city in this difficult time, and we extend our condolences to the family and friends of those lost.”

Oakland’s professional sports teams all joined in with relief efforts.

The Golden State Warriors had a moment of silence for the victims before their Saturday night game against the Phoenix Suns.

“It’s hard to comprehend, but as an organization we just want to send our thoughts and prayers to the victims, their families, friends, people who were injured,” said head coach Steve Kerr at a pregame news conference.

“I don’t know if it means a whole lot, but — I should say, I know I can’t cure the pain, but we’re thinking of you. The whole organization. The team. Everybody here at Oracle tonight,” he added. “When we have a moment of silence, we’re all with you out there. We’re all devastated today.”

The six victims that had been identified Sunday are:

Cash Askew, 22, David Cline, 35, Travis Hough, 35, Donna Kellogg, 32, all from Oakland, as well as Nick Gomez-Hall, 25, from Coronado, California, Sara Hoda, 30, from Walnut Creek, and Brandon Chase Wittenauer, 32, from Hayward.