An estimated 50,000 migrants crossed from Morocco into the Spanish enclave of Ceuta in chaotic scenes that left dozens dead. Here's what happened and why the crisis has prompted parts of Europe to tighten its borders.

Thousands of migrants entered Spain's North African enclave of Ceuta from Morocco Thursday, as local officials called for a national emergency and...

Estimates suggest up to 2,000 have entered the Spanish territory in recent days in an attempt to reach Europe.