SOUTH KINGSTOWN — Two sororities at the University of Rhode Island will have to watch from the sidelines next week as other sororities and fraternities participate in Greek Week, an annual rite with competitions and fundraisers — punishment, the university says, for allowing underage drinking at group-sponsored events.

The Sigma Delta Tau and Alpha Chi Omega sororities are also being fined $500 and they cannot hold formal events, such as dances, for the remainder of the semester, said Frances C. Cohen, URI’s dean of students and the assistant vice president for student affairs.

Cohen said the university confirmed three instances — two last fall involving Sigma Delta Tau and one this semester involving Alpha Chi Omega — in which the sororities held events with underage drinking.

She said she heard about the events and then started checking to see if what she heard was true.

“It’s a small community,” she said. “Someone says something, we ask questions and we just follow up. It’s fairly easy to discover what’s going on.”

The presidents of the two sororities could not be reached for comment yesterday. Each has about 70 members, who are also barred as individuals from attending events sponsored by other sororities and fraternities.

Cohen said one of the events occurred at the Sigma Delta Tau sorority house while the others, she believed, occurred in Narragansett at private homes.

URI has been known as a “dry campus” since 1995, when the school banned alcohol from dorms and homes on campus unless the occupants are 21 or older. The alcohol policy is the same for students who live off campus, but year-round residents in neighboring Narragansett say the change has sent student parties to their town.

The town and URI responded in 2000 with the Narragansett/URI Coalition, a board of town officials, residents, URI officials and students. Narragansett residents say the situation has improved, especially since the town adopted a tougher nuisance ordinance that posts orange stickers for the entire year on houses that have hosted large and loud parties.

Still, the issue of student drinking continues to draw attention. Two years ago, three URI students died after rowing out onto Narragansett Bay in a metal boat. The police said that the students had been drinking.

This year’s Greek Week festivities run from tomorrow through next Friday, said David P. Lavallee, a URI spokesman. Students will be raising money for the URI Foundation, a private entity that manages the endowment and major charitable contributions for the university, he said. Members of the two sororities can attend the events, but they cannot participate.

The ban on group events and other sorority and fraternity events lasts through the spring semester, at which point Sigma Delta Tau will be “watched closely” for two semesters and Alpha Chi Omega will be “watched closely” for one semester, Cohen said.

Cohen said allowing underage drinking was not typical of the two sororities, which she described as “very good groups” that “just made a mistake.”

“Neither of these sororities has been on probation for a long time, and it’s very unusual for a sorority to be in this position,” she said.

“The problem is that every year a quarter of our population is brand new and sometimes they haven’t gotten the message yet.”

redgar@projo.com