The Chinese city of Wuhan has reported six new cases of COVID-19 over the last few days which marks the first officially documented re-emergence of the virus in over a month.

Wuhan is the city where the coronavirus first broke out last December and had not recorded a new case since April 3rd. The city had since eased lockdowns and reopened schools.

The first new Wuhan case was previously asymptomatic, and the 89-year-old man had not left his residential compound since the Lunar New Year in late January.

His wife also tested positive for the virus despite showing no symptoms, the Wuhan municipal health commission said.

The residential compound has had 20 confirmed cases and experts say that the new round of infections was mainly due to previous community infections.

The new cases highlight the potential for new clusters of infections due to carriers who do not look ill or have a fever.

On Sunday, authorities also reported new coronavirus cases in northeast China, with one city in Jilin province being reclassified as high-risk, the top of a three-tier zoning system.

The city of Shulan was raised from medium to high after raising it from low to medium the day before after a woman tested positive on May 7th.

The new cases spike the overall number of confirmed new cases in mainland China to 14, which is the highest reported number since April 28.

In Wuhan, more than 20,000 people will be tested in the area where the cluster of new cases was found.

Almost 4,000 people have died across the city according to the official tally.

There is speculation that the figure could be higher as China faces questions from other countries about the accuracy of its reporting on COVID-19 cases.

This article originally appeared on Over60.