MADRID: Spain has arrested one of its top police officers after 20 million euros were found hidden in the walls of his house, as part of a probe into the country´s largest-ever cocaine bust.

Described as discreet and hard-working, Oscar Sanchez 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 told AFP without naming her.

During the raid, police found 20 million euros ($21 million) in cash hidden in the walls and ceilings of the couple´s home in Alcala de Henares, a town of around 195,000 inhabitants located some 30-kms east of the Spanish capital.

Officers also uncovered one million euros in his office, hidden in two locked cupboards, in bills of 50 to 500 euros, according to the police source.

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