MEXICO CITY (AP) — The Mexican navy said Monday it has detected a disturbing trend of migrant smugglers abandoning boatloads of people at sea off the coast of Baja California.

The Navy said that each month it has been finding an average of 10 to 12 boats, with a total of about out 150 migrants. It did not say when the discoveries began, or why the smugglers might have adopted the tactic. However, smugglers sometimes demand payment for such trips up front, leaving them little incentive to get passengers all the way to the United States.