Hyron Andrews - the former Sale second row found dead at his new team's hotel base before a Champions Cup match in France on Saturday - died of natural causes, an autopsy has found.
The 31-year-old, who joined the Johannesburg-based Lions this summer, suffered a tear in the aorta, an artery which carries blood from the heart to the rest of the body.
The rupture led to blood filling the muscle sac surrounding his heart.
Andrews was found unconscious in a shower cubicle, with investigators working on the theory that he had either suffered a fall, a heart attack or, as transpired, an aneurysm, where a bulging blood vessel breaks.
A tear in the aorta is a rare and dangerous medical condition, which can be caused by undetected high blood pressure or a birth defect.
His body is yet to be returned to his native South Africa.
Andrews' wife Maighlin, with whom he had two young sons, has asked for "respect, privacy and patience during this difficult time as the repatriation process begins", according to a statement from the Lions., external
His team-mates went ahead with their game against La Rochelle on Saturday in his honour.
The visitors were applauded into the Stade Marcel-Deflandre by home fans,, external while several of the Lions players were in tears during a minute's silence before kick-off.
Sale, with whom Andrews spent two and half seasons, also paid tribute, with director of rugby Alex Sanderson saying that his team "to a man, loved playing with Hyron and being around him".