Al Fayed was accused by more than 20 women of sexual assault in a documentary and podcast in September 2024.
One of the women featured in the documentary said she was sexually assaulted by Al Fayed at the Ritz hotel in Paris, while another woman said she had been raped by him at the Villa Windsor hotel in Paris.
Since those allegations, more than 400 alleged victims or witnesses have come forward to lawyers.
The Justice for Fayed and Harrods Survivors group said it welcomed the “significant developments” and cooperation between the Met and French authorities.
“We believe that all properties owned by Fayed should be investigated with the same thoroughness as those already searched, wherever they are located, to ensure that no potentially relevant evidence is overlooked,” the group said.
“We hope these developments represent meaningful progress towards identifying and holding to account all those who facilitated, concealed or assisted his offending, wherever they operated.”
The survivor advocacy group No One Above said: “France is treating this as organised human trafficking, led by specialists, with properties searched and evidence seized. That is what a serious investigation into a network looks like.
“Two years on, survivors are still waiting for the same from the Met. It is time the National Crime Agency took this investigation over.”