Customs officers in Gibraltar have seized 428kg of cocaine that had been secretly hidden underneath two giant cargo ships stopping at the Rock to refuel.

The drugs were attached to hidden areas below the waterline of the M/V Amaris and M/V Chao Tian Men during separate operations over recent months.

Both ships had hired diving companies to carry out routine cleaning and underwater inspections while docked in Gibraltar.

During those checks, divers spotted suspicious packages hidden near the ships’ seawater intake pipes – openings underneath the vessel used to pull seawater into the ship for cooling systems.

After alerting Gibraltar Customs, specialist divers recovered the packages from underneath the ships.

Authorities said the total haul weighed 428kg and had an estimated street value of around €29 million (£25 million).

All crew members aboard both vessels were questioned during the investigation.

However, officials said there was no evidence suggesting the sailors were involved in the smuggling operation or that the drugs were intended for Gibraltar itself.

Drug gangs frequently use this tactic by attaching waterproof packages full of cocaine underneath ships while they are docked or anchored at sea.

The idea is that the drugs can later be collected by other divers at a different port without attracting attention from the crew or authorities.

The waters around the Bay of Algeciras are considered a major hotspot for international drug trafficking due to Gibraltar’s strategic position between the Mediterranean and Atlantic.

Read more Andalucia news at the Spanish Eye.