Kate Josephs, who is currently on paid leave from her £190,000 role, admitted she had attended a drinks party at the Cabinet Office during Covid restrictions in December 2020.
She was leaving her role there as Director General of the Covid Taskforce to come to Sheffield Council as CEO.
Scotland Yard is contacting dozens of people as part of Operation Hillman, an investigation focusing on eight dates between May 2020 and April 2021, including the party Ms Josephs attended.
Police will send a formal questionnaire which has a legal status to ask people to give their account of events.
Sheffield Council said: “We have no additional information on the Met Police investigation, other than what was published in Sue Gray’s update. We cannot comment on behalf of Kate personally, or on behalf of the police.”
Last week the council announced it was bringing in an independent investigator to make a ruling on Ms Josephs but no further details have been released about who this is, what their remit is or whether they are being paid to investigate.
A cross party committee was initially set up. Last week Council Leader said: “The committee has come to the conclusion that an independent investigation is needed, and we will share further information on that after they have met next week.”
The committee met on Tuesday but there have been no further updates. The authority is currently being led by executive directors.
Ms Josephs released a statement and apologised just minutes before a national newspaper published a story about the party in January.
She had repeatedly denied to local journalists that she had been involved in any Downing Street parties.
Her statement said she had gathered with colleagues that were at work that day but it was later revealed an email was sent to 40 guests.
Police have been handed more than 300 photographs and 500 pages of evidence. Detectives may contact more people in the coming weeks, Scotland Yard said.