A canoeist has died during the annual Devizes to Westminster Canoe Race.
Race directors said they were "saddened" to report a person had died in the final stages of the race on Monday.
In a statement they added: "We are co-operating with the relevant authorities in investigating the incident fully."
The four-day race is held every Easter over a course of 125 miles (201 km) and is considered to be one of the world's toughest endurance challenges.
The race directors said their "thoughts and condolences are with the family and friends of the paddler".
David Joy, chief executive of British Canoeing, added: "I'm sure our whole community will be deeply upset to hear the tragic news this morning that a paddler has lost their life whilst competing in the Devizes to Westminster Canoe Race."
The directors of the DW race are deeply saddened to report an incident in today’s race in which a paddler lost their life. We are fully cooperating with authorities. Our thoughts are with the family and friends of the paddler. We ask that their privacy is respected at this time.— DW Canoe Race (@DWcanoerace) April 22, 2019
The first 52 miles of the race, which begins in Devizes in Wiltshire, are along the Kennet and Avon Canal and the next 55 miles are on the River Thames.
Canoeists pass through 77 locks and the race ends at Westminster Bridge near the Houses of Parliament in central London.
In 2012, Olympic rowing legend Sir Steve Redgrave pulled out of the race due to "tiredness" after completing about 87 miles of the 125-mile route.
And a year later, nearly one third of the competitors pulled out because of low overnight temperatures.