Spanish police say migrants have attempted close to 500 illegal border crossings in just one month by trying to hide on passenger and cargo boats landing on its southern coast.

As reported by The Associated Press (AP), authorities said on January 21 that they had registered these entry efforts departing from Spain’s North African enclaves of Ceuta and Melilla, after a month-long police operation last year aimed to reduce the number of stowaway migrants setting foot on mainland Spanish ports like Almeria, Malaga and Motril.

Increased patrols along both docks and boats yielded almost 500 migrants trying to clandestinely bridge the Strait of Gibraltar, mostly minors dangerously hidden inside trucks, cargo or garbage containers set to be off-loaded into Spain.