Trump Tower remains closed to the public, as more information about the 67-year-old man who died after a four-alarm fire at Trump Tower on Saturday is coming out — including his friendship with Andy Warhol.

City fire marshals Sunday are investigating what caused the blaze that killed Todd Brassner and left six city firefighters with minor injuries.

Trump Tower, which is normally open to the public 8 a.m. to 10 p.m., has been closed off. The city police department said glass is present on the floor, and it does not want the public inside while the investigation continues.

The FDNY said it happened around 5:35 p.m. Saturday of a fire at the building on 5th Ave. near East 56th St.

The city buildings department said Sunday the building did have working hard-wired smoke detectors, and that the fire department was first notified of the blaze by the detectors in the building's heating and ventilation system.

The fire started in an apartment on the building's 50th floor. Fire Commissioner Daniel Nigro said there were many pieces of furniture in the apartment, and the apartment was "virtually entirely on fire'' when firefighters.

Firefighters said they found Brassner unconscious in the apartment, and he was pronounced dead at Mount Sinai Roosevelt Hospital. A neighbor and the FDNY said the man lived in the apartment.

Property records obtained by The Associated Press indicate Brassner was an art dealer who had purchased his 50th-floor unit in 1996.

Trump Tower residents said Brassner was quiet but well-liked.

"He was a very friendly person. He greeted everyone. Very polite. That's what they said. I'm very sorry for his passing away," Trump Tower resident Sergio Bermudes said.

Brassner not only sold Andy Warhol prints but also knew the famous artist personally, even having a Warhol piece dedicated to him. Brassner is mentioned several times in Warhol's posthumously published diaries, with references including lunch dates and shared taxis. On Facebook, Brassner boasted about a portrait, seen above, that Warhol painted of him in 1975. Brassner commented that he left it in his will to the Museum of Modern Art.

His father, Jules Brassner, was also an established art dealer who had a portrait made by Warhol. When he died in 2015 in Florida, a photo of him with Donald Trump was posted on a memorial tribute website.

Court records show Todd Brassner bought his 1,100-square-foot apartment in Trump Tower in 1996, but that he eventually fell behind in his mortgage payments, in part because of medical problems and declining family support.

In 2015, Todd Brassner filed for bankruptcy. His lawyer said in court papers that the apartment's value and Todd's "substantial art collection and other valuable collectibles" were worth many times more that the value of the debt.

The value of Brassner's possessions lost in the fire is unclear. His apartment, 50C, which is a little more than ten floors below President Trump's penthouse, was valued at $2.5 million.

President Trump thanked the FDNY and praised Trump Tower as a "well built building," but he had not mentioned Brassner, instead tweeting several times about other issues since the fire.

Fire sprinklers were not present in the upper floors of Trump Tower, which contain apartments, Fire Commissioner Daniel Nigro said Saturday night. They were not required in New York City high-rises when Trump Tower was completed in 1983.

Subsequent updates to the building code required commercial skyscrapers to install the sprinklers retroactively, but owners of older residential high-rises are not required to install sprinklers unless the building undergoes major renovations.

Some fire-safety advocates pushed for a requirement that older apartment buildings be retrofitted with sprinklers when New York City passed a law requiring them in new residential highrises in 1999, but officials in the administration of then-mayor Rudy Giuliani said that would be too expensive.

Trump was among the developers who spoke out against the retrofitting as expensive and unnecessary.

Trump's business is based at Trump Tower and his residence is there, but he has spent little time in the city since taking office.

No member of the First Family was in the building during the fire, Fire Commissioner Daniel Nigro said.

Image above of Brassner via Facebook.