Dakar - Idrissa Diallo lost three children in Senegal's Joola ferry disaster, one of the worst in maritime history, but on the tragedy's 15th anniversary he has questions left unanswered.At an official ceremony in Dakar on Tuesday to remember the 1 863 people who died when the Joola ferry sunk off Senegal's Atlantic coast on September 26, 2002, Diallo vowed he would never let those killed "fade from memory".Senegal's justice system has failed to explain how so many lost their lives, the families of the victims believe, though a toxic mix of stormy weather and damaged engines are often blamed, along with massive overcrowding."The victims' families are calling for the shipwreck to be hauled up so we will know what happened," said Diallo, now president of Senegal's Joola victims' association.In Mbao, a leafy area outside the capital, Dakar, Senegalese officials joined the families before a mass of white, unmarked graves in stifling humidity, the air full of Muslim and Christian chants.The Joola was carrying close to 2 000 passengers when it sank after departing from the city of Ziguinchor in Senegal's southern Casamance region, bound for the capital. It had a maximum capacity of 536 and just 64 people survived.A ceremony of remembrance was also held in the regional city, attended by the minister for the armed forces, the public APS news agency reported.In 2003, Senegal closed an investigation into the disaster by pinning the sole responsibility on the ship's captain, whose body was never found.The legal repercussions have stretched all the way to Europe, as 18 of the victims were French. 'The courts haven't helped us' "The courts haven't helped us" in Senegal or France, said Alain Verschatse, head of the French Joola victims group. "We have had problems in identifying those responsible."In June 2016, the Paris appeals court made the same decision as their Senegalese counterparts to close a case lodged in 2003 for "involuntary homicide by deliberate violation of the rules governing care and security."In neighbouring Guinea-Bissau, home to 107 of the victims, many of whom were petty traders, tributes were paid privately."Five of our colleagues died, leaving children behind them," said Teresa Banjaque, a vegetable seller in the Caracol market in Bissau."Some families are resigned to what happened, others are not, because they never saw the bodies of their sons and daughters," she added.