MADRID — Spanish police Tuesday managed to tow a sunken submarine believed to be carrying tons of cocaine into a northwestern port and began preparations to extract its cargo.

Police were hoping to crane-lift the 20-meter (65-foot) submarine onto the dock at Port of Aldán so that they could get inside more easily, an official from the government's office in the province of Pontevedra said.

The submarine sank as police tried to intercept it Sunday in the Aldán inlet in the northwestern region of Galicia. It wasn’t clear if the crew sank it on purpose.

An international operation involving police from Spain, Portugal, the U.S., the U.K. and Brazil tracked the fiberglass vessel across the Atlantic.

The submarine was due to pass the cocaine to another vessel, but the three people on board abandoned the submarine amid rough seas off Spain last Saturday night.

Two Ecuador nationals were arrested. A third is at large.

Work on bringing the vessel ashore began Monday in bad weather and had to be suspended.

Police divers pulled out one package of cocaine from the vessel Monday.

Media reports said the vessel could be carrying three metric tons, but the official said this couldn't be confirmed yet. The official spoke on condition of anonymity in accordance with government rules.

Spanish police had been monitoring the vessel´s movements in recent days in coordination with international police.

The official couldn’t say from which country the submarine had come, but media reports said police suspected it to have set off from Colombia.

National police and the finance ministry said in a statement Wednesday that it is the first-time drug smugglers have attempted to use a submarine in Europe.

They said using submarines to smuggle cocaine is “very common” in the United States.

Authorities say the submarine could carry up to 5 metric tons.