(CNN) Hundreds of Americans who returned to the United States Wednesday from the epicenter of the Wuhan coronavirus outbreak are voluntarily quarantined at the March Air Reserve Base in southern California.

Evacuees aren't required to stay in base housing, but US Centers for Disease Control and Prevention officials said passengers were asked to stay for three days of testing and monitoring, and they are willing. If a passenger demanded to leave before the three-day period had passed, it would be a discussion "up to the highest levels within the US government," officials said during a press conference on Wednesday.

After three days without symptoms or positive tests, passengers are free to stay at the base or return to their homes, where they will be monitored throughout a 14-day incubation period.

Any passenger exhibiting symptoms will be transported to a hospital for further evaluation, the CDC said.

"We try and balance how to protect these people, how to respect their rights, how to be as least restrictive as possible and still be very careful about the evaluation that they go under so that everybody is safe," the CDC's Dr. Chris Braden said during the press conference. "This is a balance and if we can do that without a federal quarantine order that restricts people and takes away their rights, that's what we will do."

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