The boat sank between Libya and Italy, about 30 miles (50km) from the Libyan coast. A French naval ship, two trade vessels, and aerial support are involved in the search. It is unclear what the nationalities of the migrants involved are. The number of migrants travelling to Europe by land has dropped since the height of the migrant crisis in late 2015, but sea crossings remain both popular and dangerous. On Friday, the Italian coast guard rescued about 550 migrants making the journey across the Mediterranean. Doctors Without Borders, which was involved in the rescue, said that in once case it found 123 people crammed on to a single inflatable dinghy. More than 1,000 people have arrived in Europe by sea in the first two weeks of 2017, the UN refugee agency (UNHCR) estimates. Before this incident, it estimated 11 people had died or were missing. In 2016, the UNHCR said 5,000 people died trying to reach Europe by Mediterranean routes - the highest number yet.