UK police said Thursday officers would investigate a "small number" of bets made on the timing of the general election, as part of a joint probe with the gambling watchdog.
The Met had already announced that one of its officers had been arrested on suspicion of misconduct in a public office and placed on restricted duties over election betting claims.
Six other officers have now been identified as having placed bets on the timing of the poll. They are being probed by industry regulator the Gambling Commission.
In an update Thursday, the Met said its directorate of professional standards was being kept informed, while the force's own officers were also beginning to investigate cases.
"We have agreed a joint approach with the Gambling Commission, who are the appropriate authority to investigate the majority of these allegations," said Detective Superintendent Katherine Goodwin.
"There will, however, be a small number of cases where a broader criminal investigation by the police is required."
Gambling Commission chief executive Andrew Rhodes said its probe was focused on whether "confidential information" was used to gain "an unfair advantage" in bets on the election date.
"Our enforcement team has made rapid progress so far and will continue to work closely with the Metropolitan Police to draw this case to a just conclusion," he added.
'Furious'
The scandal has overshadowed the closing stretch of campaigning, as Prime Minister Rishi Sunak struggles to close the Conservatives' large poll deficit to the Labour opposition before the July 4 vote.
Sunak reiterated Thursday he is "furious" about claims at least two Tory candidates and other party figures placed bets on the timing of the ballot based on private information.
Earlier this week the Conservatives withdrew their support for the candidates.
One is married to the Tories' director of campaigns, and he has also taken a leave of absence following the allegations.
The party's chief data officer has stepped back from duties over accusations he had placed dozens of bets on the poll date.
While political bets are allowed in the UK, using insider knowledge to make them is against the law.
Sunak again refused to discuss details of the cases, including who knew of his July 4 election plan prior to the Tory leader announcing it last month.
"You'll recognise that while there are ongoing independent investigations, it's just not right for me to say anything more about that," he told broadcasters.
Labour has also become embroiled in the scandal. It dropped its support for a candidate after it emerged the Gambling Commission was investigating him on the outcome of the contest in his own seat.
Summarising the approach to the joint investigation, the Met said most cases were suspected breaches of gambling legislation and so would be investigated by the commission.
But its specialist crime unit will also probe a "smaller" number of bets "with specific features that could mean additional offences apply, for example misconduct in public office", it added.
