SAN DIEGO (AP) — A labeling error caused a woman infected with the novel coronavirus to be mistakenly released from a hospital but the oversight was noticed as she was returning to a San Diego military base where more than 200 evacuees from China are living under federal quarantine, officials said Tuesday.

Several patients who were under observation for symptoms were released from UC San Diego Medical Center on Sunday but the labeling mix-up came to authorities’ attention while they were being driven back to Marine Corps Air Station Miramar, said Dr. Christopher Braden, who leads the Centers for Disease Control and Prevention delegation in San Diego. They were isolated on the base until the test results came back, and the woman who tested positive was sent back to the hospital.

The officials received a text as they approached the base that said it was an important message, Braden said, indicating how close the infected woman was to mixing with other evacuees.

The CDC said the error occurred after it issued a negative finding Sunday on a large batch of specimens taken from people quarantined at the base. The woman had her sample taken at the hospital, where she was being observed for a cough. The hospital released her at CDC’s direction after being told that everyone quarantined had shown negative results, when, in fact, her sample was excluded from the rest of the batch.

UC San Diego Medical Center officials said Tuesday that it used pseudonyms on labels to protect patient privacy and that the CDC “used different naming protocols that were not shared with our institution.”

“It was an issue with the labeling,” Braden said at a news conference. “They have their procedures, we have our procedures. They didn’t match exactly.”

On Monday, authorities discovered that the woman tested positive for the virus, the CDC said. The hospital said the patient was doing well with minimal symptoms.

It was the 13th known case of the virus in the United States and the first among hundreds evacuated by the U.S. government from China. They are under two-week quarantines at military bases in California, Texas and Nebraska.

A second flight from Wuhan to the San Diego base arrived Friday with 65 passengers. People on both flights were split in two groups — one living in quarters used for military personnel on short-term assignments and another at a hotel for servicemembers at their families. It was unknown which group the infected patient belonged to.

The details about the mix-up happened the same day 195 evacuees were cleared to leave March Air Reserve Base in Riverside, California, after clearing their final screening. None of those evacuees tested positive.

People threw their face masks into the air and hugged, said Dr. Nancy Knight of the U.S. Centers for Disease Control and Prevention.

“They pose no health risk to themselves, to their families, to their places of work, to schools or their communities,” she told reporters. “There should be no concern about novel coronavirus from these 195 individuals. They have been watched more closely than anyone else in the United States.”

The group, which included U.S. consular officials and children, arrived Jan. 29 on a U.S.-chartered flight from Wuhan, China. The locked-down city of 11 million is the epicenter of the virus that has claimed more than 1,000 lives worldwide.

Most of the group released Tuesday planned to leave immediately, though some were staying one more day because of travel arrangements. They were headed to see family across the United States.

Among those leaving the base Tuesday was Consul General Jamie Fouss. He described how they had to check passengers against the manifest on the chartered plane in China, check bags and conduct health screenings before taking off for Alaska and later California.

The quarantine, he said, wasn’t as challenging as he thought it could be, adding the group stayed busy with evacuees running Zumba and art classes and activities for the children.

“Everybody felt like the quarantine was their civic duty to do what they needed to do to keep themselves and their communities safe,” he told reporters. “Today as we took off our masks and were given the clean bill of health, we all realized we had gone through this experience together, and we made good friends.”

Meanwhile, the FBI and Los Angeles County Sheriff’s Department said they are investigating the online posting of a fake document last month asserting the novel coronavirus was detected in the city of Carson, California. The realistic-looking document had the official logos of Los Angeles County Public Health, the CDC and the World Health Organization, and has been strongly denounced by local officials.