A yacht that capsized last May, leaving four UK sailors missing in the North Atlantic, could have been affected by structural weaknesses, a report said.
The Cheeki Rafiki crew diverted the boat after it began taking on water, but contact was then lost. Days later, the hull of the 40-foot yacht was found with its life raft still on board. There was no sign of the crew.
A Marine Accident Investigation Branch report said the vessel may have been weakened by previous groundings and subsequent repairs, according to the BBC.
Skipper Andrew Bridge, 22, from Farnham in Surrey, was lost, along with crewmembers James Male, 22, from Romsey, Steve Warren, 52, from Bridgwater in Somerset, and Paul Goslin, 56, from West Camel in Somerset.
They were returning from Antigua Sailing Week to Southampton when they capsized about 720 miles east-southeast of Nova Scotia. An air-and-sea search mission covered hundreds of miles east of Cape Cod, Mass., but was eventually called off.
The MAIB said the cause remained "a matter of some speculation" in the absence of survivors and material evidence.
"However, it is concluded that Cheeki Rafiki capsized and inverted following a detachment of its keel," the report said. "In the absence of any apparent damage to the hull or rudder, other than that directly associated with keel detachment, it is unlikely that the vessel had struck a submerged object.
"Instead, a combined effect of previous groundings and subsequent repairs to its keel and matrix (or lining) had possibly weakened the vessel's structure where the keel was attached to the hull."
It said one or more keel bolts might have deteriorated and it was "probable that the crew were fatigued and their performance was impaired accordingly.”
Since the disaster, the yacht's operator, Stormforce Coaching Ltd., said it had changed its internal policies and taken actions designed to prevent a recurrence.