Hundreds of students, their relatives and staff of the American University of Afghanistan gathered at a safe house on Sunday and boarded buses in what was supposed to be a final attempt at evacuation on US military flights, the students said.

But after seven hours of waiting for clearance to enter the airport gates and driving around the city, the group met a dead end: Evacuations were permanently called off. The airport gates remained a security threat, and civilian evacuations were ending.

“I regret to inform you that the high command at HKIA in the airport has announced there will be no more rescue flights,” said an email sent to students from the university administration on Sunday afternoon, which was shared with The New York Times.

“The scholar pilgrims who were turned away today while seeking safe passage to a better future need the help of the US government who gave them the hope they must not lose,” the American University president, Ian Bickford, said.

The email asked the 600 or so students and relatives to return home. The US troop withdrawal from Afghanistan must be completed by a Tuesday deadline, so the US military is turning from evacuating civilians to bringing its own personnel home.

The group was then alarmed after the US military, following protocol, shared a list of names and passport information of hundreds of students and their families with the Taliban guarding the airport checkpoints, the university president said.“They told us: we have given your names to the Taliban,” said Hosay, a 24-year-old sophomore studying business administration who was on the bus on Sunday. “We are all terrified, there is no evacuation, there is no getting out.”

Hosay earned a scholarship that covered half of her tuition. She wanted to get an M.B.A. and start an all-female engineering firm.

When the Taliban took over Kabul on Aug. 15, one of the first sites the group captured was the sprawling, modern American University campus. Men in traditional Afghan outfits swinging AK-47 rifles brought down the university flag and raised the flag of the Taliban, according to student and social media photos.

The Taliban posted a picture of themselves on social media standing at the entrance of a university building with an ominous message, saying this was where America trained infidel “wolves” to corrupt the minds of Muslims.

The photograph was widely shared among Afghans and sent students and alumni into hiding. They had reason to be scared. In 2016, the Taliban attacked the campus with explosives and guns in a terrorist assault that lasted 10 hours and killed 15 people, including seven students.

The university shut down its campus on Aug. 14 as word reached administrators that the Taliban were on the outskirts of Kabul. Mr. Bickford and foreign staff left Kabul for Doha that night.

Mr. Bickford said in an interview last week that he was working with the State Department to evacuate about 1,200 students and alumni. But on Friday after the deadly attack on the airport, Mr. Bickford said that effort had become much more complicated.

Mr. Bickford said the university was committed to ensuring all enrolled students would finish their degrees remotely.

The American University of Afghanistan opened in 2006, receiving most of its funding from the United States Agency for International Development, which gave $160 million. It was one of the U.S.A.I.D.’s largest civilian projects in Afghanistan.

Students said they had struggled emotionally over the past two weeks after they went from being college students to fugitives overnight.

Several students interviewed repeated a poetic saying in Dari: “Our hopes and dreams have turned into dust.”

Mohammad, a 31-year-old father of three and part-time government ministry worker, had three more courses left to finish his degree in business administration.

His job and salary are now gone. His degree is in jeopardy.

“It’s as if you throw a glass on a cement floor and your life shatters in a split second,” he said Sunday from a safe house.

Yasser, a 27-year-old political science student, said he was told in an email from the university on Saturday to report to a safe location for evacuation. But after President Biden said there were security threats to the airport, the plan was scrapped and everyone was sent home.

Early Sunday morning, Yasser received another email from the university asking him to go to a safe house at 7:45 a.m. The students were told to bring only a backpack with two outfits. Videos shared with The New York Times of the evacuation show hundreds of students carrying backpacks and waiting on the roadside. Dozens of buses are lined up.

The chitchat among students abruptly ends and someone gasps. Someone cries. The students have just been told that evacuations had been called off.

“It was a frightening day,” Yasser said. “We went there anticipating to be rescued and returned home defeated.”