The superintendent, Susan Kincannon, said in a statement that officials decided to shut the two schools plus a third, the Belton Early Childhood School, so they could thoroughly clean and disinfect the schools and buses that served them this week.

The superintendent of the Belton Independent School District, south of Waco, said that a student at Sparta Elementary School and a student at North Belton Middle School were on Frontier Airlines Flight 1143 on Monday.

DALLAS — Officials at a school district in Central Texas shut three schools Thursday after they learned that two students traveled on the Cleveland-to-Dallas flight with Amber Joy Vinson, a nurse infected with Ebola.


The two students were on the flight Monday and then attended classes Tuesday and Wednesday, the statement said. Though state and local health officials had cleared the children to return to school, their parents decided to keep them home for 21 days, the maximum incubation period of the virus.

"The health and safety of our students is my first priority," Kincannon said in the statement.

Initially Wednesday, Belton school officials emphasized to parents that the risk of exposure for passengers on the flight was low, and they had no plans to shut the schools. But Wednesday evening, Kincannon posted a message on the district's website saying that federal Centers for Disease Control and Prevention officials were "re-evaluating the health risk to some passengers" on the flight, and that as a result, they had decided to shut the schools to clean them. It was not clear what had caused that re-evaluation of the risk.

On Wednesday, officials at the disease centers had stressed that the passengers on the plane were a low-risk group. Because Vinson did not have a fever and did not have nausea or vomiting on the plane, the risk "to any around that individual on the plane would have been extremely low," Dr. Thomas R. Frieden, the CDC director, told reporters.


It was unclear if the disease centers were reassessing the risk level of the passengers, as Kincannon suggested.

In Ohio, two schools in Solon, near Cleveland, were closed Thursday after school officials learned an employee might have flown on a plane that had also carried Vinson. WKYC-TV in Cleveland reported the staff member had not been on the same flight but may have been on the same plane Vinson had flown in.

Questions continued to be raised about why, and how, Vinson was allowed to travel on either leg of her trip.

Vinson was part of the medical team that treated an Ebola patient, Thomas Eric Duncan, at Texas Health Presbyterian Hospital. She and other health care workers had been under a so-called self-monitoring regimen, and she was checking her temperature twice a day on her own.

Vinson flew from Dallas to Cleveland on Friday, because those doing self-monitoring have no restrictions on their movements or travel. Public health experts have criticized the CDC for not putting all of the hospital workers who had contact with Duncan under intensive monitoring, as opposed to the more loosely followed self-monitoring regimen.

On Sunday, while Vinson was still in Ohio, the first Dallas nurse infected with Ebola, Nina Pham, was confirmed to have the disease. Following that diagnosis, CDC officials switched Vinson's status from self-monitoring to actual monitoring by officials.

Frieden initially said that because Vinson was at that point being monitored, she should not have flown on the flight back to Dallas on Monday night. Although her temperature did not meet the fever threshold of 100.4, Vinson reported to health officials that her temperature at the time she traveled was 99.5.


But hours after Frieden spoke, it became clear that the disease centers had been aware that she was going to board the plane and allowed her to do so.

A federal health official said Vinson called the CDC before boarding the plane and reported having the slightly elevated temperature of 99.5. Because it was thought the protective gear she wore while treating the Ebola patient would have kept her safe, and because her temperature did not exceed the fever threshold, she fell into a category not covered by CDC guidelines and was not forbidden from boarding the plane.

"I don't think we actually said she could fly, but they didn't tell her she couldn't fly," said the official, who spoke on the condition of anonymity because he was not authorized to speak publicly. He said the error was on the part of the disease centers, not the nurse.