The former police chief in charge of Spain’s economic crimes unit has been arrested after officers found €20 million ($21.2 million) stashed in the walls of his house. The arrest was linked to the country’s largest ever cocaine bust, local media reported.

Oscar Sanchez Gil was arrested last week along with 15 other people, AFP reported on Wednesday, citing Spanish media. The arrests came a month after 13 tons of cocaine were found in a container of bananas seized at Spain’s southern port of Algeciras. The haul, which originated in Ecuador, was the largest ever drug shipment seized in Spain, and the second-largest in the EU, Spain’s National Police announced earlier this month.

Officers investigating the shipment quickly discovered links between the importers and Sanchez Gil, and ordered a search of his home near Madrid. They found €20 million in cash hidden in the walls of the property, and €1 million in his office, AFP reported.

Sanchez Gil’s romantic partner, who is also a police officer, was among the 15 others arrested. The detainees have been charged with drug trafficking, bribery, money laundering, corruption and membership of a criminal organization, police sources told the news agency.