BOSTON >> Seeing his injured Boston University classmates lying in a New Zealand roadway after their minivan rolled over, Evan White said he felt helpless.

"Our first impulse was to do whatever we could, but everyone had a sense of helplessness," White, a junior who riding in one of three minivans carrying the students on a hiking trip, told the school’s website. "I helped people away from the van. Others ran to a house to get help."

The Saturday morning crash killed three students and injured five others, one critically.

Meg Theriault, 21, was in intensive care Sunday at Waikato Hospital in New Zealand after surgery the previous day for her injuries. She suffered a serious head injury, a broken right arm and grazes over her body, her parents said in a statement.

"She is a fit and stubborn young woman and we know she is getting the best care," said Todd and Deb Theriault of Boston, who traveled to New Zealand to be with their daughter.

The school said 26 students were traveling in the three vans on their way to walk the Tongariro Crossing, a hike across a volcanic crater that is rated as one of New Zealand’s most spectacular.

One of the minivans drifted to the side of the road and then rolled when the driver tried to correct course near the North Island vacation town of Taupo, New Zealand police said.

The driver of one of the vans White was in saw the crash in his mirror, pulled over and backed up to the crash site, the school said. The driver of the third didn’t see the accident and continued to the initial destination.

New Zealand police official Kevin Taylor said it was unclear why the van drifted to the side of the road. He said some of the students were thrown from the vehicle, indicating they may not have been wearing seat belts.

Police spokeswoman Kim Perks said Sunday that any suggestion as to the cause of the crash at this stage is "just speculation," and that the investigation into the accident "will take some time."

"These things can happen when you’ve got international tourists on your roads, but obviously it’s a great tragedy and our sympathies go out to the families," New Zealand Prime Minister John Key said on Television New Zealand’s Breakfast show.

Killed in the accident were Austin Brashears, of Huntington Beach, Calif.; Daniela Lekhno, of Manalapan, N.J.; and Roch Jauberty, of Paris, France.

Meg Theriault, of Salisbury, Mass., was airlifted to a hospital in Taupo. In a statement Sunday afternoon, local health official Mary Anne Gill said the 21-year-old woman had surgery Saturday and was in intensive care.

New Zealand police said Sunday two other women, one 20 and the other 21, were hospitalized in stable condition. The other two injured — a 20-year-old man and 20-year-old woman — were released Saturday.

All the students except Theriault were enrolled in a BU study abroad program in Auckland, the university said. Theriault was enrolled in a study abroad program in Sydney, Australia.

Study abroad program executive director Bernd Widdig called the students’ deaths an "unprecedented tragedy," the worst to hit the program since it began in the 1980s. The New Zealand part of the program began in 2003 and involves courses at the University of Auckland and Auckland University of Technology.

Efforts by The Associated Press to reach family members of Lekhno and Brashears were unsuccessful Saturday and Sunday. A person who answered the phone at the home of Lekhno’s family Saturday declined to comment, and a message left at a phone listing for Brashears’ family wasn’t immediately returned.

White was quoted on BU’s website as saying that the students in New Zealand were staying together in Auckland after the accident.

"Last night we all dragged our mattresses into the common room and slept in the same place just to show solidarity," he said. "We are just talking about it and trying to be very open. Hopefully everyone at BU can come to terms with it too, like we’re trying to do here."

The school held a vigil Saturday night. Tori Pinheiro, a close friend of Brashears, told the few hundred who gathered that she had found an old voicemail he had left her.

"I listened to it four times, just to hear your voice," she told the crowd as she tried to fight back tears.

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Associated Press writer Nick Perry in Wellington, New Zealand, and Stephen Singer in Hartford, Conn., contributed to this report.