The Ceuta crossings have shaken Europe politically, exposing divisions over the sensitive issue of migration, the BBC's Sarah Rainsford writes.

Watch: Migrants started to return to Morocco after thousands entered Spain's Ceuta on 30 July Most of the tens of thousands of migrants who swam into the Spanish exclave of Ceuta on Thursday have now returned to Morocco, escorted to the border by Spanish soldiers and police. But the extraordinary surge of arrivals has left at least 67 people dead, their bodies pulled from the sea where they floated alongside abandoned rubber rings and flippers. This week's events have also shaken Europe politically, once again exposing divisions over the sensitive issue of migration. And they've left lingering questions about what sparked the sudden influx: whether social media posts promising an easy path to Europe just went viral or this was something more deliberate, even organised. Whatever the cause, Spain's socialist prime minister is angry with the response. Pedro Sanchez has hit out at some in the EU for "attacking" Spain in this crisis, playing politics instead of showing support. Fratelli d'Italia, the hard-right party of Prime Minister Giorgia Meloni, had been quick to post images of migrants racing through the streets of Ceuta.