Spain has arrested one of its top police officers after €20m (£17m) was found hidden in the walls of his house, as part of an investigation into the country’s largest-ever cocaine bust.

Óscar Sánchez Gil was until recently the head of the fraud and anti-money laundering division of Spain’s national police force in Madrid.

Officers arrested him last week along with 15 other people, including his romantic partner, who is also a police officer in the Madrid region, a police source said without naming her.

During the raid, police found the €20m, in cash, hidden in the walls and ceilings of the couple’s home in Alcalá de Henares, a town of about 195,000 inhabitants located 18 miles (30km) east of the Spanish capital.

Officers also found €1m in his office, hidden in two locked cupboards, in bills of €50-500, according to the police source.

The couple have been charged with drug trafficking, money-laundering, corruption and membership of a criminal organisation after last week appearing before a Madrid court, which remanded them in custody, a judicial source said.

Spanish media said the arrests were linked to the seizure last month of 13 tonnes of cocaine that arrived in the southern port of Algeciras from Ecuador’s largest city Guayaquil – a drug-trafficking hub – hidden among crates of bananas.

Police said the drug bust – which they only announced last week – is the largest-ever haul of cocaine in Spain and “one of the largest seizures in the world”.

The container was destined for a Spanish importer based in the south-eastern coastal town of Alicante “who had been receiving large quantities of fruit imported from Ecuador for years”, the authorities said.

Police searched several homes and offices in Madrid and Alicante after the cocaine seizure. These operations uncovered links between the importer and Sánchez Gil, according to Spanish media reports.

He was already under suspicion by his colleagues who had tapped his phone, daily newspaper El Mundo reported.

The father-of-three, who is in his 40s and lives in a brick house protected by metal gates, is suspected of having worked for the drug traffickers for “at least five years”, a source told the newspaper.

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During these years, he allegedly provided them with information on the surveillance of containers in Spanish ports, which enabled them to avoid checks, according to a source close to the investigation.

While his lifestyle was not ostentatious, the large sums of money found in his home led police officers quoted by El Mundo to compare his house “to that of Pablo Escobar”, the notorious Colombian drug baron who was shot dead by police in 1993.

A nephew of Escobar once said he found a plastic bag with money worth $18m hidden in the wall of one of his uncle’s houses.

Part of the money Sánchez Gil amassed in recent years was laundered through the purchase of crypto-currencies and a large fleet of private hire vehicles registered in the name of one of his relatives, El Mundo reported.

Spain is a main entry point for drugs into Europe because of its close ties with former colonies in Latin America such as major cocaine producers Colombia and Peru, and its proximity to Morocco, a top cannabis producer.