Spain's government delegation in Ceuta said at least 18 people died Thursday, though officials did not immediately explain the circumstances. According to the AP, bodies were seen floating in the water as rescue and security operations continued.
Video from the area showed large groups of migrants entering Ceuta through the Tarajal border area, with many arriving by swimming around coastal barriers separating Morocco from Spanish territory. Most appeared to be young men, though families with women and children were also among those crossing.
Spanish authorities said Morocco is cooperating with efforts to regain control of the border. Spain's Interior Ministry said Moroccan police have intercepted numerous migrants attempting to cross and that both governments are working to return those who entered the territory illegally as quickly as possible.
Authorities have not identified a single cause for the sudden surge, though Ceuta officials have pointed to a recent Spanish Supreme Court ruling that limits the immediate return of migrants who arrive by sea without due process. Some migration advocates, however, questioned whether the ruling alone could explain the dramatic increase, arguing many migrants would likely have been unaware of the decision.
The crisis has reverberated beyond Spain. Italian Prime Minister Giorgia Meloni threatened to suspend Italy's participation in the Schengen open-border agreement with Spain, saying the move would be necessary "to defend our borders and ensure the safety of our citizens."
Ceuta, a small Spanish territory on Morocco's Mediterranean coast, has long been one of Europe's most active migration flashpoints.
Migrants from across Africa regularly attempt to reach the enclave by swimming from Morocco or scaling the heavily fortified border fence in hopes of gaining entry into the European Union.
Spain's Interior Ministry said nearly 3,000 migrants had entered Ceuta by land or sea this year through mid-July, before this week's crossings dramatically increased those figures.
Fox News Digital has reached out to Spain's Embassy in Washington, the Department of Homeland Security, the Center for Immigration Studies and the Migration Policy Institute for comment.
The Associated Press contributed to this report.