Britain's Metropolitan Police had received material in August about the deaths of the Princess of Wales and her partner Dodi Al-Fayed in the car crash, which media reports suggested related to claims the Special Air Service was involved.
New material had been reportedly passed to the police by an army source after the allegations were made by the former wife of an SAS soldier, named only as Soldier N.
The police said that having conducted a "scoping exercise" there was no basis to open a criminal investigation. A statement from the police said its assessment included "taking statements from a number of individuals and reviewing records".
It said the investigating officers were given "unprecedented access" to Special Forces Directorate records. "Every reasonable line of enquiry was objectively pursued in order to fully evaluate any potential evidence.
The final conclusion is that whilst there is a possibility the alleged comments in relation to the SAS' involvement in the deaths may have been made, there is no credible evidence to support a theory that such claims had any basis in fact," the statement said.
"Therefore the MPs are satisfied there is no evidential basis upon which to open any criminal investigation or to refer the matter back to HM Coroner," it concluded.
A 2008 inquest had found the couple had been unlawfully killed as the crash in the de l'Alma tunnel occurred partly due to the "gross negligence" of the driver.
Egyptian tycoon Mohamed Al Fayed, Dodi's father, was "disappointed but not discouraged" by the outcome, his solicitor Simon McKay said.
He called the scoping exercise "the latest whitewash in a 16-year cover up". Princess Diana, the former wife of the Prince of Wales and the mother of princes William and Harry, was 36 when she died in the crash with Al Fayed, 42.
Henri Paul was driving when their hired Mercedes crashed into a pillar in the tunnel soon after the couple had left the Ritz Hotel in Paris and were pursued by paparazzi on motorbikes.
Al Fayed's bodyguard, Trevor Rees-Jones, was the only survivor. The paparazzi pursuit, Paul's drink-driving and a lack of seatbelts had contributed to the deaths, the inquest jury had ruled.
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