Tens of thousands of migrants who crossed into Spain’s tiny Ceuta territory have returned voluntarily to Morocco. Their return on Friday came a day after the influx triggered chaos in the city in North Africa and reignited the immigration debate in Europe and beyond. At least 57 migrants died on the journey. Ceuta’s president put the number of migrants at 60,000, which was equivalent to 70% of the territory’s population. But most of them soon went back, the Spanish government said, after the sudden arrival of so many people sparked a humanitarian crisis.