NEW HAVEN  It was well after midnight, and the invitation-only party for Yale University undergraduates was reaching a peak. In the upscale nightclub Elevate, not far from campus, more than 100 students in semiformal attire were on the dance floor as Journey’s “Don’t Stop Believing” pulsed over the sound system. In a throwback to childhood, a buffet table held platters of chicken nuggets and French fries.

But then the lights came on and about a dozen police officers and state liquor control agents, acting on a tip about under-age drinking, entered the club early on Saturday. Partygoers say the officers, two of them in riot gear and armed with assault rifles, ordered students to sit on the floor as they checked IDs, and for the next hour silenced polite questions with expletives and threats of arrest.

Some students were crying even before an officer used a Taser gun on one sophomore; the police said the student had assaulted three officers. Another student said an officer had punched him.

Raids on bars are not unusual these days in New Haven, where huge crowds in a cluster of downtown nightspots have lately turned rowdy. But the sweep last weekend has reverberated far beyond Elevate, a second-floor club on Crown Street, angering students and perplexing administrators in the Gothic halls on campus.