OAKLAND — Ghost Ship master tenant Derick Almena and his second-in-command, Max Harris, were arrested Monday and charged with 36 counts of involuntary manslaughter in conjunction with the Dec. 2 Ghost Ship fire that killed three dozen people.

Alameda County prosecutors found the pair hoarded flammable materials from floor to ceiling in the warehouse, created an illegal party space, and even blocked one of only two exits from the second floor the night of the fatal fire.

“The paying guests at the event were faced with a nearly impossible labyrinth of the defendants’ making to get out of that building,” said District Attorney Nancy O’Malley at a news conference Monday. “Almena and Harris’ actions were reckless and they created the high risk of death.”

Prosecutors announced the arrests a little more than six months after the inferno but declined to speak about whether others, including warehouse landlord Chor Ng, will face criminal charges. Friends and families of victims on Monday called for Ng to be charged, blaming her for owning a building many called a “deathtrap.”

In court documents, Alameda County district attorney investigator Cristina Harbison said Almena held the lease for the warehouse and lived inside illegally, encouraging his sub-tenants to create living spaces with “non-conventional building materials,” such as wooden sculptures, pianos and furniture.

O’Malley said Almena and Harris “very purposefully allowed floor-to-ceiling quantities of highly flammable materials…that created a deadly and dangerous space.” O’Malley said.

Almena, 47, also advertised the space for three years as a music venue and social gathering place without permits, Harbison wrote. Once he began using the warehouse to host parties, he was obligated to install proper fire prevention systems. Witnesses also told investigators he was repeatedly warned about the dangers, but failed to act, Harbison wrote.

The investigator released the first details about the fire’s origin, saying it started in the northwest corner of the first floor of the warehouse, but because there was so much damage the “exact cause is undetermined.”

Almena was arrested in Lake County, while Harris, also known as Max Ohr, was arrested in Los Angeles County on Monday morning without incident, DA spokeswoman Teresa Drenick said at an afternoon news conference in Oakland.

In an initial court appearance, a Lake County judge set bail at $1.8 million. Almena, with his signature goatee, sat shackled in court wearing a white-and-green striped jumpsuit over an orange short-sleeved shirt, answering “No,” when a judge asked him if he had any questions. The short appearance ended with the judge saying Almena would need to be returned to Alameda County within five days. He was transferred and booked into Santa Rita Jail in Dublin on Monday night. He is scheduled to be arraigned Thursday.

On the Lake County jail website, Almena’s home address was listed as Upper Lake and he listed his profession as “set designer/stage build.” Harris was booked into Los Angeles County jail and held on $1 million bail. He did not make a court appearance.

If convicted on all 36 charges, Almena and Harris each face up to 39 years in prison, Drenick said.

Almena and Harris are also defendants in civil lawsuits filed on behalf of the fire victims.

DA O’Malley told reporters Almena and Harris “knowingly created a fire trap.”

Court documents also revealed that 27-year-old Harris planned the party Dec. 2 and in his preparation blocked off one of two exits from the second floor, which “effectively reduced the upstairs guests to a single point of escape” down the makeshift front staircase made of wood pallets. Harbison said Harris was Almena’s “creative director,” collecting rent, mediating disputes among tenants and acting as an intermediary between Almena and the building owners.

The pair also altered the interior of the warehouse by building a bathroom, cutting a doorway into a wall, cutting a hole in the roof and opening a previously sealed window in an adjacent building wall, according to the probable cause statement.

“Their reckless actions were the proximate cause of the death of the 36 individuals trapped inside the warehouse when the fire started,” O”Malley said.

Almena’s defense team released a statement Monday saying they plan to “vigorously defend” their client.

“We believe that these charges represent no less than a miscarriage of justice, and we are confident that this attempt to make a scapegoat out of our client will fail,” attorneys Jeffrey Krasnoff, Tony Serra and Kyndra Miller said.

Criminal defense attorney Dan Horowitz, who has been following the case, called the charges appropriate.

“The property owner could have been charged but the jury may have hung on that defendant and it would’ve put a cloud over a very good case against the other defendants so it was a judgment call,” Horowitz said.

Stanford Law professor Robert Weisberg said charges against Almena and Harris were “inevitable.”

“In theory they could even be second-degree murder charges, but involuntary manslaughter seems a no-brainer,” Weisberg said. “Charges against the owner seem plausible, as well as charges against others who helped run the place or the event. One might infer that some peripheral actors are getting a chance to cut deals to testify against the major actors.”

Thirty-six people, all but one of them attending a dance party in the upstairs of the warehouse, died in the blaze. For family and friends of the fire victims, the arrests bring little comfort.

“I just wish that it wasn’t happening at all,” said 60-year-old Enid Dias, a relative of one of the fire victims, 32-year-old musician Brandon Chase Wittenauer. “It doesn’t give any relief to me. I just wish it never happened.

“I kind of think it’s gotten harder, because we’re going through a first everything without him,” she said. “Our first Memorial weekend, our first Easter, our first Mother’s Day. How do you say happy Mother’s Day? You can’t, because it’s not happy.”

Eric Bateman, who performed in the band Easystreet with both Chelsea Faith and Travis Hough — who also died in the fire — said he has “very complicated feelings” about the charges.

“How can you go after the people who lived there,” he said, “who in their hearts and minds had a space for performances and the community, and not go after the landlord for not upgrading the electrical system or turning a blind eye to what existed there?”

Both O’Malley and Oakland Mayor Libby Schaaf, however, said Almena and Harris conspired to cover the fact that people were living in the warehouse from authorities and city officials. In one police officer body camera video obtained by this news agency, Almena is seen telling an officer in 2014 that no one lives at the warehouse.

“The reckless and deceptive actions of Derick Almena and Max Harris claimed 36 innocent lives,” Schaaf said. “For years, they worked hard to escape legal scrutiny and deceive city officials. Because of their callous disregard for human life, they deserve to be prosecuted to the full extent of the law.”

A father of three, Almena helped decide who lived and worked in the warehouse while collecting rent that was passed on to Chor Ng. Tenants described Ng as an absentee landlord, whose son Kai and daughter Eva took care of managing the warehouse.

Harris was the doorman the night of the deadly fire and ran a tattoo shop inside the Ghost Ship.

“I greeted almost every single person who walked through that door,” Harris said in December, referring to the night of the deadly fire. “And I’m usually the one who says goodbye to them at the end of the night as well.”

The Ghost Ship, at 1315 31st Ave., was zoned and permitted only as a warehouse, but was filled with live-work spaces for artists. Electricity was provided from a wire running through a hole in the wall from an auto body shop next door and extension cords criss-crossed the space like spider webs.

City documents show police officers, firefighters, and code enforcement and building inspectors had dozens of interactions with the collective and the people who lived there, yet none took any action that could have led to its closure.

Emails and correspondence between tenants and the Ngs showed early knowledge of the haphazard electrical system, and sources told this newspaper that the fire was sparked by an overburdened electrical system.

Harris told this newspaper in past interviews that the Ngs blew off his concerns. “Kai Ng totally sidestepped my expression of needing stability,” he said in a phone interview. “I said it was terminal and was getting worse, and he just asked for more money.”

Staff writers Marisa Kendall, Eric Kurhi and Zach Jordan contributed to this report.