Groupama sailing team suspended racing from the fifth leg of the Volvo Ocean Race after the mast broke just above the first spreader.
The crew are all safe, with the boat around 60 nautical miles south of Punta del Este.
"We just lost the rig now, all the crew is safe. We are working to stabilise the rig on the boat. Not easy," skipper Franck Cammas told Race HQ.
"We suspend the race now and have a look at what doing. We are 59 miles to Punta del Este."
Groupama 4 was holding a narrow lead over Puma in the leg from Auckland to Itajaí in southern Brazil when the incident was reported to Race control around 1540 UTC.
Volvo Ocean Race will release more information as it becomes available.
- 1 Apr 2012At a glance: April 1, 2012
- 31 Mar 2012Telefónica reach Cape Horn, pull in for repairs
- 30 Mar 2012Round the Horn ... at last
- 30 Mar 2012PUMA stalk Groupama as Cape Horn looms
- 29 Mar 2012Temporary weather window opens for leading pair
- 29 Mar 2012Groupama and PUMA in tactical battle on approach to Horn