Metropolitan Police chief Dame Cressida Dick confirmed the force was investigating allegations of coronavirus rule breaches in Downing Street and Whitehall.
GB News understands Sue Gray's report into "partygate" will not be published until the conclusion of this investigation.
Dame Cressida told the London Assembly’s Police and Crime Committee: “We have a long-established and effective working relationship with the Cabinet Office, who have an investigative capability.
“As you well know they have been carrying out an investigation over the last few weeks.
“What I can tell you this morning is that as a result of the information provided by the Cabinet Office inquiry team and, secondly, my officers’ own assessment, I can confirm that the Met is now investigating a number of events that took place at Downing Street and Whitehall in the last two years in relation to potential breaches of Covid-19 regulations.”
She added: "Metropolitan Police Commissioner Dame Cressida Dick said: “The fact that we are now investigating does not, of course, mean that fixed penalty notices will necessarily be issued in every instance and to every person involved.
“We will not be giving a running commentary on our current investigations.”
But there will be updates at “significant points”, she added.
She said “several other events” that appeared to have taken place in Downing Street and Whitehall had also been assessed, but they were not thought to have reached the threshold for criminal investigation.