Police estimated several thousand Amherst students celebrated the annual event near several apartment complexes, beginning at noon Saturday and going well into the night, resulting in at least 44 arrests by early Sunday, the (Springfield) Republican reported.
Police said other Blarney Blowout festivities were calm and problems were reported only at the apartment complexes north of the Amherst campus.
Police Capt. Jennifer Gundersen said four officers sustained injuries and a number of young people also were injured in the confrontation.
She said charges filed against the 44 revelers ranged from failure to disperse and inciting a riot, assault with a dangerous weapon, breaking and entering, disorderly conduct, liquor law violations, and assault and battery on police officers.
University spokesman Ed Blaguszewski denounced the actions, saying university officials would review the situation and take action as appropriate, including possibly suspending or expelling students.