The World Health Organization has recorded 65 cases of the coronavirus among staff based at its headquarters, including five people who worked on the premises and were in contact with one another, an internal email obtained by Associated Press shows.

The UN health agency said it is investigating how and where the five people became infected – and that it has not determined whether transmission happened at its offices. WHO’s confirmation Monday of the figures in the email was the first time it has publicly provided such a count.

“To my knowledge, the cluster being investigated is the first evidence of potential transmission on the site of WHO,” Dr Michael Ryan, the agency’s chief of emergencies, told reporters on Monday after AP reported on the internal email.

The email said about half the infections recorded so far were in people who had been working from home. But 32 were in staff who had been working on premises at the headquarters building, where more than 2,000 people usually work and the agency says it has put in place strict hygiene, screening and other prevention measures.

In the email, which was sent to staff on Friday, Raul Thomas, who heads business operations at WHO, noted that five people – four on the same team and one who had contact with them – had tested positive for Covid-19. That could indicate that basic infection control and social distancing procedures in place may have been broken.

“We have had some cases that have been associated with the premises. We do have some cases in the last week that are linked together,” Maria Van Kerkhove, WHO’s technical lead on Covid-19, confirmed on Monday.

Of the linked cases, she added: “There are possible ways in which they were infected outside of the premises. So we’re still doing the epidemiologic investigation with that.”

Two weeks ago, Van Kerkhove had said there had been no transmission at headquarters to that point but added that the agency was monitoring it. WHO, which is coordinating the global response to the pandemic, had previously said that staff members had been infected but never provided a number or details.

“As per standard protocols, these colleagues are receiving the necessary medical attention and are recovering at home,” the email on Friday said. “These last five cases bring the total reported number of affected members of the Geneva based workforce to 65 since the beginning of the pandemic.”

According to the email, 49 of the overall cases had occurred in the last eight weeks, “thus very much in line with the situation being reported in Geneva and the surrounding areas”. He added that “a higher number of cases among those who telework might have gone unreported”. The timing of the other 16 cases was not clear.

The revelation comes amid a surge of cases in Europe, host country Switzerland, and the city of Geneva, in particular.

The email did not specify who was infected, but a WHO employee with direct knowledge of the situation who spoke on condition of anonymity because she was not authorised to speak to the press said the five linked cases included a member of the WHO director general’s leadership team who is also an infection control specialist.

Thomas’ email was sent after other WHO officials raised concerns that people who had been in contact with the group were still working in the Geneva building and potentially exposing others to Covid-19, the employee said.

The senior manager reportedly held several in-person meetings at WHO in early November before testing positive last week. The person, contacted by AP, referred all comments to the WHO media office.

“We have not yet established whether transmission occurred on campus, but are looking into the matter,” Farah Dakhlallah, a WHO spokeswoman, said in an email to AP.

WHO has faced repeated criticism of its handling of the pandemic. US President Donald Trump accused the UN agency of “colluding” with China to hide the extent of the initial outbreak.

In June, the AP found WHO publicly lauded China for its speed and transparency, even though private meetings showed WHO officials frustrated that the country sat on releasing critical outbreak information.

The email obtained by AP said enhanced measures to “reduce our risk profile” were being considered.

“Finally, members of the workforce are reminded that physical meetings, including gatherings in common areas or in the cafeteria, are strongly discouraged and should only take place where absolutely necessary,” it added.

Elsewhere in Geneva, restaurants are among many public venues that have been closed to prevent the spread of Covid-19.

Last month, Thomas told WHO employees the agency was restricting access to its Geneva headquarters to critical staff, including senior directors, their assistants and management officers.

“All members for the workforce are reminded to always keep proper hand hygiene, respect physical distancing standards (at least one metre) and wear masks, when distancing is not possible,” he wrote.

In normal times, an estimated 2,400 people regularly work at WHO’s seven-story headquarters overlooking Geneva. As the pandemic has swelled in the area, staff have been encouraged to work from home when possible. Non-staff visitors have been required to wear masks, and access to the building has been curtailed.

And ahead of WHO’s weeklong meeting of its member states last week – which was mostly virtual – staff were told in an internal email to take extra precautions, including mask-wearing in public places.

On Monday, from a vast meeting room at the headquarters, WHO Director General Tedros Adhanom Ghebreyesus and other officials were taking part in a session of the agency’s latest executive board meeting, which was largely conducted by video conference.

He was returning from a two-week self-quarantine at home after coming into contact with a person who tested positive. Because Tedros did not show any symptoms himself, he was not tested for Covid-19 but stayed at home out of an abundance of caution.