South Korean officials reported that nearly 100 people thought to be cured of the novel coronavirus have tested positive again.

Jeong Eun-kyeong, director of the Korea Centers for Disease Control and Prevention said during a briefing that the virus may have "reactivated" in the patients rather than them becoming reinfected, Reuters reported .

Health officials in the country said it is unclear how or why this has happened in the 91 patients, but an epidemiological investigation is underway.

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Approximately 10,450 cases of COVID-19 have been reported in South Korea, and 208 people have died. According to a Johns Hopkins database , more than 7,110 patients have recovered from the virus.

The KCDC reported 27 new cases of the coronavirus on Friday, the lowest number since late February. It also reported seven new deaths, according to Reuters.

Whether a person can become infected with COVID-19 twice has been unknown since the start of the pandemic. The Centers for Disease Control and Prevention says that the body's immune response, including how long someone is immune to the virus, "is not yet understood."

The agency said patients who had been diagnosed with a virus similar to COVID-19 "are unlikely to be reinfected shortly after they recover, but it is not yet known whether similar immune protection will be observed for patients with COVID-19."