Princess Diana

The car's chauffeur also was killed in the crash, police said.

A fourth person in the car, one of the princess' bodyguards, was seriously injured and freed from the wreckage, police said.

The crash occurred shortly after midnight in a tunnel along the Seine River at the Pont de l'Alma bridge in the capital's 8th district, while paparazzi -- the commercial photographers who constantly tail Diana -- were following her car on at least one motorcycle, police said.

Several motorcyclists were detained for questioning after the crash, police said. A badly damaged motorcycle was taken from the scene of the accident by police.

Witnesses heard crash

An American witness, Mike Walker, told CNN the car in which Diana was traveling "looked like it hit the wall."

Two other Americans visiting Paris heard the crash and ran to the scene. Joanna Luz and Tom Richardson, both of San Diego, told CNN they were walking along the Seine when they heard a bang and squealing tires under the bridge.

They described the car as a dark blue Mercedes, with the passenger side airbag deployed, facing oncoming traffic.

They also said they believed at least one cameraman was following the car, saying that what appeared to be a professional photographer was on the scene less than 15 seconds after the crash.

"His equipment was very professional -- his camera was a foot and a half tall," Luz said. "It definitely was not a tourist camera."

Early calls to British newspapers found none with reporters assigned to follow Diana in Paris. However, CNN Paris Bureau Chief Jim Bittermann said that would not be unusual; the British papers often rely on freelancers who are willing to go to great lengths to get an exclusive photograph of the princess.

Car destroyed

Christopher Dickey, the Paris bureau chief for Newsweek magazine, was at the scene when the Mercedes was removed from the tunnel. Its windshield was cracked, its roof collapsed, and the front of the car crunched back to the windshield.

A wrecking crew had great difficulty recovering the car, Dickey said, because even the wheels wouldn't move. "Only the trunk of the car appears to be intact at this point," Dickey said. In the end, the car was lifted out with a crane.

Bittermann said the highway, one of several high-speed arteries into the heart of Paris, typically has very little traffic around midnight Saturday.

There is no barrier between incoming and outgoing traffic, Bittermann said; if a car went out of control it would be nearly certain to swerve into oncoming traffic.

The crash trapped several people in a pileup, Radio France Info reported. Police cars and vans with flashing lights filled the site outside the tunnel and officers blocked off the area.

The car was apparently traveling without an escort.

Diana, Fayed dined earlier in evening

Reports said that Diana and Fayed, 42, were dining at the Ritz Hotel in Paris before the accident. Fayed's family owns the Ritz Hotel chain; the car's chauffeur was also reported to be a Ritz employee.

Diana, whose divorce from Britain's Prince Charles became official last year, had been on vacation in the south of France with Fayed last week. It was believed to be her third romantic vacation with Fayed.

Speculation surrounding Diana and the Egyptian millionaire has been rampant ever since she was spotted embracing Fayed on a Mediterranean cruise earlier this month.

Fayed and the princess are said to have met about 10 years ago, when he played polo against Prince Charles, the heir to the British throne.

Fayed lived lavish lifestyle

Films that Fayed has produced or co-produced include the 1981 Oscar-winning "Chariots of Fire," "The World According to Garp," "F/X" and "Hook."

Reportedly a multi-millionaire, Fayed had homes in London, New York, Los Angeles and Switzerland as well as a garage full of luxury cars. His 1994 marriage lasted just eight months.

Fayed's father, self-made billionaire Mohamed Al-Fayed, owns London's fabled Harrod's department store, the Hotel Ritz in Paris and has 11 homes around the world.

Mohamed Al-Fayed had been friendly with Diana's father, the late Lord Spencer.

Diana and Charles' two sons, Princes William and Harry, are believed to be vacationing with Charles at the royal family's Scottish home at Balmoral. Buckingham Palace said Charles had been notified of the accident.

Diana was due back in Britain on Sunday and had been expected to see her sons at her London home at Kensington Palace.

Paris Bureau Chief Jim Bittermann, Reuters and The Associated Press contributed to this report.