The Chinese capital Beijing has put more neighbourhoods under lockdown and boosted testing as it tries to contain an outbreak of coronavirus.
The city has seen more than 100 new cases in the fresh outbreak, the World Health Organization (WHO) says.
For more than seven weeks Beijing had only registered cases from people travelling in from abroad.
New clusters of coronavirus are "always a concern", said Mike Ryan, the WHO's emergencies programme head.
"But what we do like to see is an immediate response to that and comprehensive set of measures," he added.
What do we know about the new cases?
The fresh outbreak has been linked to city's largest wholesale market, Xinfadi.
Local media reports say the virus was discovered on chopping boards used for imported salmon at the market, prompting major supermarkets in Beijing to pull the fish from their shelves.
The general manager of the market has been dismissed, along with other local officials.
In his comments though, the WHO's Mike Ryan was cautious about the cause of the outbreak, saying the suggestion it was carried on salmon or its packaging was only a "hypothesis".
Other health experts have pointed to cross-contamination as being a more likely source.
The chief epidemiologist of China's Centre for Disease Control and Prevention (CDC) said the virus strain found in Beijing did not resemble the type circulating across the rest of the country, and the WHO has also urged China to share the genetic sequencing of the strain.
What's being done to combat the outbreak?
The market was shut early on Saturday and restrictions imposed on nearby neighbourhoods.
By Monday Beijing had set up nearly 200 testing sites and contacted about 200,000 people who had visited the market since the end of May, state news outlet Xinhua reported.
Volunteers at security checkpoints tested residents' temperatures.