Detectives investigating alleged breaches of the Covid-19 restrictions in Downing Street and Whitehall have begun to interview people as witnesses, while enquiries continue.
Scotland Yard has confirmed more than 100 questionnaires have been sent out to date asking the recipients about their participation in the alleged gatherings - including to prime minister Boris Johnson.
Officers are reviewing all material available in detail, including returned questionnaires.
The surveys offer those quizzed a chance to explain their involvement - and anyone asked to answer one is given seven days to respond.
Further individuals were identified and sent questionnaires after more information came to light, and the police say they reserve the right to contact others as inquiries progress.
The Met has not yet made any referrals to the ACRO Criminal Records Office for the issuing of fixed penalty notices (FPN).
A Met spokesperson said: “Every questionnaire response is being assessed alongside all available evidence, and should this reach the evidential threshold, then referrals will be made.
“This investigation involves a significant amount of investigative material; the serving of over 100 questionnaires and the need to individually assess every response.
“The offences under consideration comprise a number of elements and the legislation itself changed between the event dates.
“We are progressing the investigation as quickly as possible.”
Downing Street has been contacted for comment.