Scotland Yard said it had concluded its latest investigation but would make no formal statement before tomorrow.
Diana, Dodi and chauffeur Henri Paul died after their Mercedes crashed in a Paris tunnel on August 31 1997.
It emerged in August that the police were looking at claims that the couple were murdered by a member of the British military.
Scotland Yard said it was "scoping" the information and "assessing its relevance and credibility".
It was understood the allegation was made by the former parents-in-law of a former soldier based on information that the ex-soldier talked about in the past, according to a source.
It is believed that the information was passed to the Metropolitan Police via the Royal Military Police.
Scotland Yard said: "The Metropolitan Police Service (MPS) received material on August 16, 2013 in relation to the deaths of Diana, Princess of Wales and Dodi Al Fayed.
"The MPS undertook a scoping exercise to assess the relevance and credibility of that information.
"That scoping exercise is now complete.
"Assistant Commissioner Mark Rowley wrote to all parties and provided them with a summary report of the scoping exercise.
"In that letter AC Rowley made an undertaking that, in order for them to consider the report, the MPS would not make a formal statement until Tuesday, December 17."
Sky News reported that the Metropolitan Police had said there was "no credible evidence" that the SAS was involved.