After a multiple-vehicle accident on Friday claimed the lives of four Yale University students, their schoolmates spent the weekend attending memorial services and mourning their deaths.

Two students remain hospitalized after the crash, which occurred when their sport utility vehicle collided with a tractor trailer that had jack-knifed on an icy Interstate 95 in Fairfield, Conn., according to state police.

Two other Yale students injured in the chain-reaction crash were discharged from area hospitals Saturday.

The collision occurred shortly after 5 a.m. Friday as the nine students, all but two of them members of the Bulldog baseball or football teams, were returning to campus from a Delta Kappa Epsilon fraternity event in New York City in a 1999 Chevrolet Tahoe.

Yale junior Adam P. Wolf, whose roommate died in the crash, said all the students involved in the collision were either pledges or members of the fraternity.

Friends of the victims said the nine students had been participating in a series of pranks and social events sponsored by the Delta Kappa Epsilon fraternity, which is known as DKE or “Deke.”

A university spokesperson said she believed last week was the fraternity’s “rush week.”

Founded at Yale in 1844, DKE has counted five American presidents among it members, including both Bushes.

According to state police, there are no preliminary indications that any of the drivers had been using alcohol or drugs.

The three students who died at the scene of the accident were sophomore Kyle M. Burnat, 19, of College Park, Ga., sophomore Andrew K. Dwyer, 20, of Hobe Sound, Fla. and the driver of the vehicle, junior Sean R. Fenton, 20, of Newport Beach, Calif.

Sophomore Nicholas G. Grass, 19, of Holyoke, Mass., died early Saturday afternoon from injuries sustained during the accident.

First-years Cameron A. Fine, 18, of Phoenix, Ariz., Christopher W. Gary, 18, of Nazareth, Pa., Brett D. Smith, of Papillion, Neb., sophomore Zachery A. Bradley, 19, of Alexander, Ark. and senior Eric W. Wenzel, 21, of Garden City N.Y., were injured in the crash.

Students said news of the accident has sent shock waves through the Yale campus, where students recently returned from winter break.

“The atmosphere has been drastically different,” said Yale sophomore Lindsay E. Page. “A lot of people were close to the young men involved and even if you did not know them personally, you have been touched by the sadness of the accident.”

Flags on Yale’s campus have been lowered to half-staff in memory of the students who were killed and injured. University officials cancelled or postponed all home athletic events Friday night and convened a service after notifying students of the accident in a campus-wide e-mail Friday afternoon, students said.