2 Chainz Album Party Shut Down in NYC ... But Who's to Blame?

2 Chainz is pointing the finger at the fire marshal for shutting down his new album listening party, and the event promoters are blaming cops ... but NYC officials are calling BS.
NYC Dept. of Buildings officials tell TMZ ... their reps were at the ASA Gallery in Soho Wednesday night, not fire marshals. They say the 2 Chainz event -- for his "Pretty Girls Like Trap Music" album -- was way over capacity, but promoters were told they could continue if they got occupancy down to 74.
Instead of complying, the promoters decided to cancel ... at least that's NYC's take. Chainz maintained on social media it was the fire marshal.
Sources connected to event organizers say they were told 200 people was the max -- and planned accordingly -- but cops were already there before the party began and turned away fans. We're told promoters tried to negotiate with cops, but THEY killed the party.
FDNY tells us they had nothing to do with it. 2 Chainz says he's looking for a bigger venue for take 2 on the party.
We reached out to NYPD ... no word back so far.