Three people have been killed after a high-powered speedboat smashed into a concrete causeway outside Venice at the end of a race that started in Monte Carlo in Monaco.
A fourth person was badly injured in the crash, which happened in darkness on Tuesday night.
The boat was attempting to establish a new speed record for traveling from Monte Carlo to Venice, a distance of more than 1,000 nautical miles, and was reportedly traveling at 80mph when the accident happened.
Italian authorities denied early reports that two of the dead were Britons.
The fatalities included Fabio Buzzi, 76, a 10-time powerboat world champion.
The boat had been racing at high speed for more than 18 hours when it crashed into the causeway at the Bocca di Lido, one of three channels that lead from the Adriatic into the Venetian lagoon.
The causeway is part of a vast engineering project known as Moses, which consists of barriers placed on the sea floor that are designed to rise up and prevent Venice from flooding during high tides and heavy rain.
“An investigation is underway into the causes of the accident,” Alberto Pietrocola, a commander with the Italian Coast Guard, told the Telegraph. “I can confirm that no British citizens were involved, contrary to earlier reports.”
Maurizio Darai, who was on board another boat that was monitoring the race, said: “We found the speedboat almost entirely submerged in the water, only the prow was sticking out.”
Mr Buzzi was a legend in the powerboat world, designing and racing his own vessels, and had decades of experience.
The two other fatalities were named as Luca Nicolini, an Italian, and Eric Hoorn, a Dutchman.
A fourth person on board the boat, Mario Invernizzi, was thrown clear of the wreck and survived. He was taken to hospital with serious injuries.
Mr Buzzi was the founder of FB Design, a company which specialises in building high performance powerboats.
Boats designed by the company have won more than 50 world championships and set 40 world speed records.
“I learned more about designing and building boats from Fabio Buzzi than anyone else in the world,” John Cosker, the founder of a powerboat building company in Florida who worked with Mr Buzzi in the 1990s, told the website speedonthewater.com. “He knew more about designing boats than anyone I have ever met.”