The rocky outcrop known as Isla de Tierra—part of the Alhucemas Islands archipelago—measures 1.7 hectares (4.2 acre) and is just 30 meters (100 feet) off the Mediterranean coast of Morocco at low tide.
The migrants swam or waded across to the island early Sunday, according to the regional office of the Interior Ministry located in the Spanish enclave of Melilla, which lies on the north African coast.
Three minors and 17 women were part of the group. Another 19 migrants reached the archipelago Wednesday.
Around the same time Sunday morning, a group of some 60 migrants tried to rush a fence separating Melilla from Morocco. They were repelled by the fence and Spanish border guards "acting in collaboration with Moroccan security forces," the regional office statement said.
Every year migrants from Africa try dangerous crossings to reach Spanish territory illegally in hope of gaining work and a better life. Authorities suspect people smugglers were involved with the latest groups, regional government leader Abdelmalik El Barkani said.