As two students remained hospitalized Monday, classmates and teammates struggled to accept the loss of four students who died in a car accident early Friday.

Senior Eric Wenzel, 21, of Garden City, N.Y., was in critical condition Monday evening and remains on a ventilator in Bridgeport Hospital, Jonathan Edwards College Master Gary Haller said in an e-mail to students. Wenzel underwent his first physical therapy session Monday afternoon and his injuries were healing, Haller said.

Freshman Brett Smith, 18, of Papillion, Neb., was reported to be in serious condition Monday evening at Norwalk Hospital, downgraded from critical condition. He remained in the intensive care unit, hospital officials said. In an e-mail to Ezra Stiles College students Monday night, Master Traugott Lawler reported that Smith had made progress and was receiving antibiotics for a minor fever.

Three Yale students were killed instantaneously and one died later in the hospital after their sport utility vehicle crashed into a jackknifed tractor-trailer rig on Interstate 95 early Friday morning. Sophomore Kyle Burnat, 19, of Atlanta; sophomore Andrew Dwyer, 19, of Hobe Sound, Fla.; and junior Sean Fenton, 20, of Newport Beach, Calif., were pronounced dead at the scene of the accident. Sophomore Nicholas Grass, 19, of Holyoke, Mass., died Saturday at St. Vincent’s Medical Center in Bridgeport.

Sophomore Zachery Bradley, 19, of Alexander, Ark., was discharged from Bridgeport Hospital Monday, and freshman Cameron Fine, 18, of Phoenix, was released from St. Vincent’s Medical Center in Bridgeport Saturday morning, hospital officials said.

Freshman Christopher Gary, 18, from Nazareth, Pa., was discharged Saturday from Norwalk Hospital.

Also involved in the accident were Armando Salgado, 33, and two other motorists who were taken to area hospitals with minor injuries, police said. Salgado, who drove the Arrow Trucking Company freightliner into which the students’ SUV crashed, was discharged Saturday from St. Vincent’s.

The nine passengers of the SUV were either pledges or members of Delta Kappa Epsilon fraternity. They were among 23 members returning from a fraternity event that is held every year during rush, DKE president Nicholas Sinatra ’03 said in a written statement.

The freshmen went down early Thursday night via train, Sinatra said. The upperclassmen followed in three cars shortly after 10 p.m. that evening.

The group convened at around 2 a.m. Friday morning at a bar, Sinatra said.

“Those DKEs that were of age went in while the others waited outside,” he said.

At around 3 a.m. the upperclassmen made plans to drive the freshmen back to New Haven, because the first train from Grand Central Terminal to New Haven was not scheduled to depart until 5 a.m., according to Sinatra.

The students returned in three vehicles. The nine students involved in the accident were in the second car to leave for New Haven, a 1999 Chevrolet Tahoe, which left 30 minutes after the first car. Sinatra left for New Haven in the third car around 3:45 a.m., he said.

“All three cars had designated drivers,” Sinatra said. “My car stopped at McDonald’s at about 4:30 a.m. on the highway to have breakfast. We then drove up the highway a few more miles when we saw the horrible accident.”

Sinatra said the accident must have happened only shortly before his car arrived at the scene, because traffic was still flowing northbound.

“We saw wreckage on both sides of the highway before we drove up to the SUV carrying our dear friends,” Sinatra said. “We pulled over to help and walked within 15 feet of the SUV and witnessed a scene I do not wish to describe.”

Sinatra said paramedics were still trying to save some of the passengers, so state troopers asked Sinatra and his friends to leave the scene of the accident. Some DKE members went to Bridgeport Hospital to find out what happened, he said.

“The rest of the day was a blur of hopping from one hospital to the next and comforting each other as well as consoling the devastated parents,” Sinatra said.

Many questions remain concerning the deadly accident, as investigators from the state Department of Transportation, the state police, the National Transportation Safety Board, as well as national DKE officers, piece together evidence and interview witnesses in an attempt to reconstruct the events that culminated in the deaths of the four students.

“There’s a lot of holes. There’s a lot of questions people have,” state police Sgt. J. Paul Vance said.

Police said weather conditions could have been a factor.

“It was cold and precipitation was falling,” Vance said.

Other details of the accident that remain to be determined are the speeds at which the vehicles were driving, the lighting conditions on the interstate, and whether the driver of the freightliner logged his required hours of sleep.

Vance said investigations, including toxicology tests, could be concluded within four to six weeks.

The accident, which involved four vehicles in total, occurred near Exit 24 at the Bridgeport-Fairfield town line shortly after 5 a.m., police said. The tractor-trailer rig, driven by Salgado, was heading northbound on I-95 in the center lane. Salgado lost control on the icy interstate and jackknifed into the median. The tractor of the tractor-trailer detached partially and crossed the concrete barrier that separates the two sides of the highway, Vance said.

Vance said at that point a car, driven by Lucilo Cifuertes, 46, and another tractor-trailer heading southbound, driven by David Zappone, 37, collided with the tractor of the first truck.

The first accident resulted in minor non-life-threatening injuries.

The rear flatbed trailer of the first tractor-trailer came to a rest on the highway, blocking the northbound lanes, police said.

Minutes later, the northbound SUV full of Yale students smashed into the flatbed trailer that was blocking the northbound traffic lanes. Three students died on the scene, and six others were rushed to area hospitals.

Yale altered Friday’s athletics schedule because of the accident. Friday’s basketball game was postponed until Saturday night and a swim meet was cancelled.

In the hours before the fatal accident, state police said there had been a number of other accidents reported on I-95 in Norwalk, New Haven and Westport, when there was snow on the highway. There was also a car rollover reported northbound about 4 a.m. in the area where the fatal accident occurred an hour later.

Sinatra tried to express the collective grief felt by his fraternity brothers at the loss of four of their own.

“The accident Friday morning on I-95 was a horrible tragedy that was deeply felt by DKE,” he said. “The brothers of Delta Kappa Epsilon ask that the Yale community keep our fallen brothers and their families in your thoughts and prayers.”