Police searching for Madeleine McCann will begin activity in Portugal.
The disclosure comes amid reports Portuguese authorities have given permission for sites in Praia da Luz, where the toddler went missing, to be searched.
Met Police Assistant Commissioner Mark Rowley said he would be unable to provide details of activity.
But he said he believed it “will occur in the coming weeks”.
A letter was sent to media editors amid speculation about excavation work.
Madeleine McCann was three when she went missing from a holiday apartment in Praia da Luz, Algarve, in May 2007.
A request to search a number of sites was among a series of requests made to police in Portugal by British detectives working on the case, according to reports.
Mark Rowley said he had discussed the case with his opposite number in Portugal and highlighted the “high levels of interest” that activity would generate in the British media.
But he said Portuguese police do not provide the media with updates on current investigations.
He adds that “activity will cease” if police in Britain provide information or reporters “cause any disruption to their work in Portugal”.
Mark Rowley also said the processing of requests had been “more bureaucratic and slower than we would wish”.
But he asked media editors to respect the requests of Portuguese authorities as they carry out the work.
“We do not want to undermine our prospects of providing Mr. and Mrs. McCann with answers in this tragic case,” he added.
The development comes after the seventh anniversary of Madeleine McCann going missing was marked on Saturday.
Gerry McCann, Madeleine’s father, expressed his family’s gratitude that the Metropolitan Police team investigating Madeleine’s disappearance was now moving on to a “very active” phase in their investigation.
Kate McCann also disclosed last week that she returns to the Portuguese resort where her daughter disappeared to “walk those streets” and “look for answers” once or twice each year.
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