5:29 PM PT -- Law enforcement sources directly familiar with the case tell TMZ ... Howie mentioned the Xanax found in his pocket during the arrest, allegedly telling police, "It's Xanax. I take it before I go on stage."
5:16 PM PT -- We've learned the woman claiming assault against Howie is an ex-girlfriend.
Law enforcement sources tell TMZ ... the "Collide" singer was busted Friday after he allegedly got into an argument with a woman at a hotel in Manhattan's Financial District. Things got so heated that cops were eventually called ... and the woman reported that Day had grabbed her, thrown her around, and wrapped his hands around her throat and squeezed.
When cops arrived, we're told 8 Xanax pills were found in Howie's pocket. The woman, whose relationship to Howie is unclear, reportedly sought medical attention and got a protective order against Howie as well.
He was booked on charges ranging from assault with intent to cause physical injury, criminal obstruction of breathing and possession of a controlled substance. Howie was reportedly arraigned Saturday, where he's said not to have entered a plea. He bailed out on $500 bond.
This, of course, is a huge deal ... seeing how Howie was arrested in April 2018 for a similar alleged incident -- only that one was caught on video. In surveillance footage, obtained by TMZ, you can see Howie shove his then-girlfriend, Carrie