After hundreds more migrants perished last weekend in the deadly Mediterranean passage to Europe, one Catholic expert insisted that the root causes of migration need to be addressed.

"The real tragedy is that these deaths are preventable," said Bill O'Keefe, vice president of government relations and advocacy for Catholic Relief Services.

"We need to ensure safe passage for all refugees and migrants, but also address the reasons people are migrating in the first place," he stressed.

The United Nations' refugee arm reported on Tuesday that 245 were feared dead or missing from two shipwrecks in the Mediterranean Sea over the weekend, adding to an already steep death toll for migrants headed for Europe from North Africa.

One of the boats carrying migrants, a rubber dinghy, sank on Friday with 132 on board, and "some 50 people were rescued" while 82 others "are feared dead or missing," the U.N. Human Rights Council said.

Meanwhile, another ship sank off the coast of Libya on Sunday. Seven people were reportedly rescued by the Libyan Coast Guard, while 163 others were feared dead or missing.

Overall, more than 1,300 migrants have died trying to cross the Mediterranean from North Africa in 2017, the UNHRC said, while "over 43,000 refugees and asylum seekers have used the Central Mediterranean route to reach Italy," including over 6,000 just last weekend.

Conditions on the boats have become even more dangerous than before, as migrants face overcrowding on small crafts along with other perils.

"I am profoundly shocked by the violence used by some smugglers," Filippo Grandi, the UN's high commissioner for refugees, stated on Sunday. He added that crowding on the ships – and the conditions of the ships themselves – are serious concerns.

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"The increasing numbers of passengers on board vessels used by traffickers, with an average of 100 to 150 people, are also alarming and the main cause of shipwrecks, and risks are increased by the worsening quality of vessels and the increasing use of rubber boats instead of wooden ones," Grandi stated.

For migrants headed to Europe from sub-Saharan Africa, the Mediterranean Sea crossing is not the only perilous aspect of journey north. Some don't even make it to the coast but are trapped and sold as slaves in Libya and Niger, according to the International Organization for Migration and reported by Al Jazeera.

Leonard Doyle, chief IOM spokesman in Geneva, stated back in April that migrants have "become commodities to be bought, sold and discarded when they have no more value."

The migration routes to Europe are deadly, but there's a serious reason why people are still choosing to make this trip, O'Keefe explained.

"Poverty, conflict, unresponsive governments, and climate change are driving millions of people from Africa, the Middle East, and Asia to seek safety and opportunity in Europe," he said.

"The US must do more to negotiate solutions to conflict, fund programs to fight hunger and poverty, and help the poor adapt to climate change."