By Phil Stewart

WASHINGTON (Reuters) - The Pentagon was gripped by an Ebola scare on Friday after a woman vomited in a parking lot, triggering authorities to send in a HazMat team and shut off part of the military complex before concluding she did not have the deadly virus.

The Pentagon initially said in a statement that the woman indicated she had "recently visited Africa."

But her employer told Reuters she had not traveled abroad recently and local county health authorities later acknowledged that her travel history had been uncertain.

"Based on the public health investigation, which included the travel history of a woman who became ill this morning in a Pentagon parking lot ... medical authorities are confident that she does not have Ebola," the local health authorities said in a statement.

The public health investigation also included questioning of the woman by medical staff, they said.

There has been mounting alarm in the United States about the risks from Ebola after two nurses who cared for an Ebola patient in Texas contracted the virus. Ebola has killed more than 4,500 people, mostly in West Africa.

The incident outside the Pentagon triggered emergency protocols. The Arlington County Fire Department sent emergency medical aid and a HazMat response team, and the Pentagon closed down part of the parking lot and one of its entrances.

Since the woman had briefly boarded a bus before falling ill, the vehicle and its passengers were stopped for about four hours, one passenger recounted to Reuters. The passengers included uniformed Marines headed to a Marine Corps ceremony attended by top brass and U.S. Defense Secretary Chuck Hagel.

The Pentagon later said the passengers were being screened.

"An investigation of this person and her illness led investigators to believe at the time that they were potentially dealing with a person with an infectious disease," it said.

(Reporting by Phil Stewart; Editing by Mohammad Zargham, Frances Kerry and Ken Wills)