Muslim migrants aboard a migrant-smuggling vessel threw 12 Christian migrants overboard, likely killing them, after a fight broke out on the craft carrying 105 people from Libya to the Italian coast, according to a CNN report made Thursday. Italian authorities later intercepted the boat and once on land arrested 15 individuals for their alleged involvement in the attacks.

Others were targeted as well, but they formed a human chain and fought back against the Ivorian, Malian and Senegalese Muslims who wanted to toss them from the ship, Italian authorities said. The reason for the dispute is unclear, but the 12 Nigerian and Ghanaian nationals were specifically targeted because they were Christian.

More than 170,000 people illegally crossed the Mediterranean in 2014, and the 3,200 who died set a record. Ten times more people have died since January this year than during the same period last year, according to the New York Times. Smugglers, already known for abandoning migrants in the middle of the Mediterranean, have become increasingly violent. Smugglers fired warning shots near two European vessels to retake control of a smuggling boat from which rescuers had just rescued 250 people.

Smugglers have taken advantage of the fair weather brought by the change of seasons in the Mediterranean to send more migrants in dangerously overcrowded boats on their perilous journey of more than 300 miles. The rickety boats are known to capsize and lose power midjourney. In a separate incident on Thursday, only four of 45 people were recovered after a boat sank during its voyage across the Mediterranean.

Italy has seen the most migrants off its coasts, and the Italian coast guard and navy are overburdened by the massive humanitarian crisis. Italian authorities have appealed to the European Union for assistance, but Foreign Minister Paolo Gentiloni said Italy had “not had an adequate response from the EU," according to the BBC. In November, Frontex, the EU’s border management agency, took over from Italy, but the country continues to bear the weight of the crisis.