PULLMAN, Wash. (AP) _ Washington State University officials on Thursday sanctioned six fraternities because of their alleged participation in an alcohol-fueled melee that injured two dozen police officers.

University President Sam Smith declared: ``The party's over.''

The six houses will be barred from rushing new freshman in August unless they can demonstrate their members did not contribute to last weekend's off-campus rampage.

More severe sanctions could follow, including lifting of chapter charters.

A preliminary investigation indicates ``a significant number'' of individuals in the six houses contributed to the violence against police.

Members of the mob pelted police with beer cans and rocks during the five-hour melee. About three dozen people, including 23 police officers, were injured.

The fraternities facing sanctions are: Alpha Gamma Rho, Alpha Kappa Lambda, Kappa Sigma, Lambda Chi Alpha, Phi Kappa Tau and Sigma Alpha Epsilon.

Smith said the sanctions are the beginning of a campaign to transform the isolated Eastern Washington campus.

``I am sick of the party school image that refuses to go away,'' he said.