Her soon-to-be-touring partner Spears showed up at the event and joined Minaj on stage, but the resulting crowd surge left a number of fans feeling faint and they had to be carried out by security guards, according to E! Online.
A source tells the publication, "(It) was complete pandemonium. Six people were carried out after hyperventilating. They literally fainted when Britney walked onto the stage where Nicki was hanging.
"People were crowd surfing to get to the stage. Screams were so loud for Nicki and Brit you couldn't hear the music. Bouncers couldn't hold the crowd back."
Spears later told fans about her night out with Minaj in a post on her Twitter.com page, writing, "Hanging with my girl Nicki Minaj at her after party at The Factory. Love you girl. - Britney."
Meanwhile, the two new pals have teamed up in the studio to record a remix of Spears' new single Till The World Ends. The track also features Ke$ha, who co-wrote the song.