Officials at a Dallas hospital apparently failed to follow federally issued guidelines last week when they sent home the patient later diagnosed with the first case of the Ebola virus on U.S. soil.

The Dallas Morning News reports that Thomas Eric Duncan arrived in the emergency room of Texas Health Presbyterian Hospital late on the evening of Sept. 25 complaining of a fever and abdominal pain. When questioned by a nurse, Duncan admitted that he had been in Liberia as recently as the prior week.

At that point, according to an Aug. 1 protocol issued by the Centers for Disease Control and Prevention (CDC), Duncan should have been placed in an isolation unit and tested for Ebola immediately. However, the News reports that key medical personnel at the hospital were not told of Duncan's travel history, and he was given antibiotics and sent home, a decision that could have exposed dozens of people to the virus for several hours.

Duncan's condition later worsened, and he returned to the hospital Sunday in an ambulance. At that point, the CDC protocol was followed. The Ebola diagnosis was confirmed by health officials Tuesday.

Dr. Mark Lester, the southeast clinical leader for hospital parent company Texas Health Resources, acknowledged Wednesday that Duncan had voluntarily provided his travel history. However, Lester said, "that information was not fully disseminated." Lester did not say who he thought might be responsible for the miscommunication.

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Hospital officials defended the initial handling of Duncan, issuing a statement describing his fever as "low-grade," and insisting "his condition did not warrant admission." They added that they are still investigating why Duncan's travel history was not conveyed to the doctors who sent him home. Hospital epidemiologist Dr. Edward Goodman told the Associated Press that the patient did not show the riskier symptoms of vomiting and diarrhea.

KDFW reported late Wednesday that Duncan's condition had been upgraded to serious. Goodman wouldn't comment on drugs being used to treat the patient, but he said that there isn't any more ZMapp available. ZMapp is an experimental drug that was used on two previous Ebola patients.

Meanwhile, a nine-member team of federal health officials has begun tracking anyone who had close contact with him after Duncan fell ill on Sept. 24. The group of 12 to 18 people included three members of the ambulance crew that took Duncan to the hospital and a group schoolchildren. They will be checked every day for 21 days, the disease's incubation period.

Neither the ambulance crew nor the children showed any symptoms and were being monitored at home. It was not clear how Duncan knew the children, but his sister told the AP he had been visiting with family, including two nephews.

The CDC sent a team to the airport in the Liberian capital, Monrovia, on Wednesday to make sure health officials there are screening passengers properly. All people traveling from the outbreak zone are supposed to be checked for fever and asked about their travel history before being allowed to leave. Plastic buckets filled with chlorinated water for hand-washing are present throughout the airport.

"There were no signs of any disease when the gentleman boarded the flight," said Dr. Tom Kenyon, director of the CDC's Center for Global Health. "This was not a failure of the screening process at the airport."

Since the man had no symptoms on the plane, the CDC stressed there is no risk to his fellow passengers.

The Dallas apartment complex where Duncan was believed to be staying was cordoned off Wednesday, and the management was turning away visitors. TV cameras lined the fence of the parking lot, and at least one helicopter hovered overhead.

The Associated Press contributed to this report.

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