Six months after a devastating fire ripped through the cluttered Ghost Ship warehouse in Oakland, killing 36 partygoers, police have arrested the master tenant of the venue and his assistant on charges of involuntary manslaughter.

Alameda County District Attorney Nancy O’Malley formally announced charges at a late-afternoon press conference.

The two suspects, Derick Almena and Max Harris, were each charged with 36 counts of involuntary manslaughter.

A probable cause statement filed on Monday said that the duo filled the building with flammable materials from 'floor-to-ceiling', thereby creating a deadly 'labyrinth' which meant victims had little chance to escape.

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Ghost Ship arrests: Police on Monday arrested Derick Almena (pictured left in his mugshot from June 5) and Marx Harris (right) in connection to the deadly December fire at the Ghost Ship warehouse in Oakland

Gutted: This December 3, 2016, file image from video provided by KGO-TV shows the Ghost Ship Warehouse after the fire that killed 36 people

Authorities say Almena, 46, leased the warehouse and illegally sublet space for artists to live and work. He also held for-profit concerts at the warehouse, which was not licensed for entertainment.

Harris, also known as Max Ohr, lived at the Ghost Ship and is accused of helping plan the December 2, 2016, electronic music concert where the deadly inferno broke out.

That night Almena skipped the rave, instead spending it with his wife Micah Allison and their three children at a hotel, reportedly leaving Harris in charge.

The San Jose Mercury News reported, citing an unnamed source, that Almena was taken into custody in Lake County, while Harris was apprehended in Los Angeles.

Former residents of the makeshift artists' colony run by Almena said the warehouse was a death trap with few exits, piles of driftwood and a labyrinth of electrical cords.

Photos of the interior taken before the fire showed a hodgepodge Bohemian scene of Tibetan prayer flags, Christmas lights and scores of wooden statues of Buddha, the virgin Mary, Jesus Christ, elephants and dragons that sat atop pianos and turntables.

Victims: Top row L-R Donna Kellogg, Nick Gomez-Hall, Travis Hough, Nicole Siegrist aka Denalda Nicole, Chelsea Faith Dolan, Barrett Clark. Second row from top: Feral Pines, Micah Danemayer, David Cline, Chase Wittenauer aka Nex Iguolo, Pete Wadsworth, Jonathan Bernbaum. Third row from top: Ara Jo, Cash Askew, Sara Hoda, Draven Mcgill, Michela Gregory, Johnny Igaz. Fourth road from top: Alex Ghassan, Hanna Ruax, Edmond Lapine, Em Bohlka, Jennifer Kiyomi Taouye, Jenny Morris. Fifth row from top: Ben Runnels, Alex Vega, alana Kane - Jennifer Mendiola, Amanda Allen (Kershaw), Griffin Madden, Joey Matlock aka Joey Casio. Bottom row: Vanessa Plotkin, Nicholas Walrath, Jason McCarty aka Jalien Adrian, Billy Dixon, Wolfgang Renner, Michelle Sylvan

Almena (pictured in an old mugshot, left) was staying in a hotel with his wife and three children on the night of the fire. His aide, Harris (right), was reportedly left in charge of running the party

The ground floor had RVs and nooks used as living spaces that were rented out to tenants, while the upstairs had space for concerts.

In early May, The San Jose Mercury reported that Oakland firefighters toured the Ghost Ship and spent hours inside the building in September of 2014, with one of them allegedly likening the cluttered space to 'a museum' and another describing it as an 'amazing space.'

It was also revealed in February that city officials in California were warned about the Oakland 'Ghost Ship' warehouse more than 22 times in the years leading up to the deadly fire that killed 36 in December.

Police officers shut down a 'drug-fueled' rave at the warehouse nearly two years before the blaze and continuous complaints flooded in about the property in the 30 years leading up to the tragedy.

the fired raced through the building, trapping guests inside. For those who survived, it was largely a matter of luck that when the first cries of 'fire' were heard, they were able to find their way through smoke and darkness or were near enough to a door or already outside

The upstairs floor inside the warehouse had space for concerts and parties

The venue featured floor-to-ceiling wooden decorations that quickly caught fire during the 2016 blaze

Ornate couches, a piano and lamps are seen inside the artists' colony in this undated photo taken before the devastating fire

Officials have said they had no idea the building was used as a residence. But on February 2, 2015, a person called the police claiming to be locked out of the warehouse and told a responding officer that 'this is a warehouse that is also an illegal shared housing'.

The officer reported that the issue was resolved and left, the documents reveal.

Records show Oakland police officers responded to several landlord-tenant disputes in recent years.

And less than three weeks before the fire, Oakland city inspectors received complaints about the warehouse being remodeled into residences.

Another complaint was lodged on November 14 about an illegal interior building structure, records show.