by Nick Watt, ABC News
New questions are being raised about the death of Princess Diana, and the conspiracy theories are swirling again.
A British investigation, due out Thursday, will say that the princess was being spied on by the U.S. Secret Service.
The report by former Metropolitan Police Chief John Stevens will say that U.S. Secret Service agents were bugging Diana's phone the night she died.
Exactly why they were doing that remains a mystery.
Indeed, there's a lot of mystery surrounding Diana's death.
The 36-year-old princess; her friend, Dodi Fayed, 42; and driver Henri Paul died when their Mercedes crashed inside Paris' Pont d'Alma tunnel on Aug. 31, 1997.
The car was being followed by media photographers.
Fuel to Conspiracy Theorists' Fires?
A tragic accident or the culmination of a sinister plot? Conspiracy theories have swirled for nearly 10 years.
Lord Stevens, once Britain's top cop, has spent three years searching for the truth. He is expected to reveal some tantalizing tidbits, including those bugging allegations.
But why would the United States bug Princess Diana?
"She actually had put herself in a very high-profile political position. I think it probably would be odd if she wasn't being monitored," said Ingrid Seward, the editor in chief of Majesty Magazine.
For example, Diana was a vocal campaigner for a ban on land mines.
"Perhaps it's that link that made her of interest to outside intelligence services," said Crispin Black, a former British government intelligence analyst. "That doesn't mean it was something sinister."
U.S. officials will not comment on the report's expected accusations.
Report Will Confirm Driver Drunk
Stevens will also reportedly confirm that Diana's driver that night was an agent of French intelligence, the DST.
"If I were an FBI man or a DST man or a MI5 man, I would make sure I had drivers in all the big hotels in the big cities working for me," Black said.
Despite that, Stevens will reportedly conclude this was a tragic car accident, plain and simple.
Crucial to Stevens' conclusion that it was an accidental death is a fresh DNA test on Paul's blood that proves that he was drunk and that the blood tested was actually his.
One rampant conspiracy theory suggests the DNA samples were switched.
But will his word be enough?
"Nobody wants to think that somebody so gorgeous, so troubled, so interesting could have died such an ordinary death," Seward said.