Anne Schuchat, director of the Centers for Disease Control (CDC), testifies during a House Energy and Commerce hearing in Washington, D.C., on Wednesday, Sept. 25, 2019.

A mistake in the lab led U.S. health officials to release an infected coronavirus patient from a San Diego hospital, the Centers for Disease Control and Prevention confirmed Tuesday.

The patient was evacuated from Wuhan, the epicenter of the new coronavirus outbreak, on a government-chartered flight last week. Two such evacuation flights carrying more than 200 Americans in total arrived last week at Marine Corps Air Station Miramar in San Diego.

Upon arrival, all passengers were subject to health screenings and a 14-day federal quarantine order at the Miramar site, officials from the CDC said. Four evacuees exhibited symptoms of the new coronavirus, now named COVID-19, and were transferred from the Miramar facility to a UC San Diego Health facility for isolation and treatment, UC San Diego Health said in a statement.

On Sunday, UC San Diego Health said, CDC officials said all four evacuees tested negative for the virus. The patients "were discharged and returned to federal quarantine at MCAS Miramar."

However, CDC officials later told UC San Diego Health that further testing Monday morning revealed that one patient in fact tested positive for the virus.

CDC Principal Deputy Director Anne Schuchat was asked at a news briefing Tuesday whether the incident calls into question the effectiveness of the diagnostic test.

"With other cases around the country that we're evaluating, we have been doing serial tests to understand whether they're still infectious," she said. "In this circumstance, that's not what happened. It turns out there was probably a mix-up and the original test wasn't negative."

The patient has now returned from quarantine at the Marine Corps base to the UC San Diego Health facility "for observation and isolation until cleared by the CDC for release."

The CDC is investigating how many individuals the patient may have been in contact with, CDC's Schuchat said. It is unclear how much time the patient spent at the Miramar facility.

"The preliminary information I had is that there was very limited contact," she said. "But I think that's being reassessed at this point."