Why is Ceuta a migration flashpoint and how were so many people able to cross from Morocco?

From the publisher

What has happened and where? Border controls between Morocco and the tiny Spanish territory of Ceuta appeared to break down in the past week, allowing tens of thousands of people to cross on to the Spanish side in chaotic and dangerous scenes that resulted in dozens of deaths. The number of arrivals was more than two-thirds the size of the ordinary population in Ceuta, where a humanitarian crisis was playing out on Friday. Spanish officials said on Monday that an estimated 69,500 people who had arrived late last week in Ceuta had returned to Morocco. As of Monday, about 2,500 people who had made the crossing were believed to still…

The source's own excerpt, unedited