THE HAGUE, Netherlands — An international police operation led by Spanish authorities dismantled a major criminal network involved in trafficking migrants, drugs and weapons across the Western Mediterranean, the European Union police agency Europol and Spain’s Civil Guard announced Friday.

The takedown of the group underscored the highly professional and highly lucrative nature of migrant and drug smuggling operations in the narrow sea that separates Europe from North Africa.

Spanish authorities described the network as one of the “largest criminal organizations specializing in maritime human trafficking in the Mediterranean.”

The announcement came a week after irregular migration to Spain was thrust into the international spotlight when tens of thousands of migrants stormed into the Spanish North African territory of Ceuta in a surge blamed on rampant online rumors about an open border. Most of the migrants have since returned to Morocco.

Europol said the network it helped to dismantle “arranged storage, transport, refueling, maritime transfers, vessel maintenance, and counter-surveillance services” for other smuggling gangs.

The agency headquartered in The Hague, Netherlands, supported and helped to coordinate the operation that Spanish authorities launched in 2023 involving Spain’s Civil Guard and National Police, as well as French, Polish and Portuguese law enforcement and Europol.

The arrests came as a result of an “action day” on June 16, Europol said, that led to 77 arrests in Spain and one in Algeria and the seizure of 18 motorboats, including high-speed vessels, drugs, satellite phones, a handgun and more than 25,000 euros ($29,000) in cash.

Video released by Spanish authorities showed police arresting suspects and counting large stacks of 50 euro bills found during their searches.

The network had a two-way smuggling route between Algeria and Spain, transporting drugs to the African nation and cramming boats with migrants for the return trip to Spanish coastal towns, Spain’s Civil Guard said.

“They are considered responsible for at least 64 migration operations through which they allegedly smuggled more than 2,000 migrants into Spain, obtaining profits exceeding 24 million euros,” the Civil Guard said in a statement.

Four of the network’s alleged leaders were among those arrested, the Civil Guard said.

“They used extremely violent methods to protect the vessels and resist law enforcement,” the Civil Guard added.

The network operated a fleet of boats including “ghost speedboats, vessels designed to avoid registration and detection, which are prohibited in Spain,” Europol said.

Investigators believe suspects involved in the migrant smuggling “perpetrated sexual assaults, physical abuse, and placed migrants in inhuman conditions in makeshift housing,” the agency said.