There has been a sudden resurgence of coronavirus cases in Beijing, with officials reporting more number of new cases and prompting them to reinstate strict lockdown measures.

The officials reported new cases in the Xinfadi market, the biggest wholesale food market in Asia, accounting for 80 percent of Beijing’s farm produce supply.

The market has been shut and tens of thousands of nearby residents are being tested for the virus. The Xinfadi market is 20 times larger than the seafood market in Wuhan, the epicenter of the COVID-19 outbreak.

Xu Hejiang, a spokesman at the Beijing city government, said, “The risk of the epidemic spreading is very high, so we should take resolute and decisive measures.”

On Sunday, the officials conducted nearly 76,500 tests, out of which 59 individuals tested positive, according to Gao Xiaojun, a spokesperson for the Beijing public health commission.

Recently, the officials collected 8,950 samples at Xinfadi, said Gao, adding that 6,075 tested negative so far.

A sudden surge in new cases has prompted governments in some cities and provinces to reinstate tough measures, warning their residents against non-essential travel to the capital.

On Sunday, the World Health Organization (WHO) said Chinese officials have informed about the recent surge in cases, its source, and its extent. The global health organization reinforced the need for thorough investigations.

The WHO said, “Genetic sequencing from humans and environmental samples is ongoing, and WHO encourages the release of these sequences as soon as possible. WHO understands that genetic sequences will be released as soon as possible once further laboratory analyses are completed.”

Epidemiologist Yang Peng, who is with the Beijing government, said that a DNA sequencing of the coronavirus showed the recent Xinfadi outbreak could have come from Europe. “Our preliminary assessment is the virus came from overseas,” Peng said. “We still can’t determine how it got here. It might’ve been on contaminated seafood or meat, or spread from the faces of people inside the market.”