Spanish authorities have ordered the holders of about 3,000 secret bank accounts in Switzerland to pay tax on the undeclared funds by the end of the month, a newspaper said Wednesday.

The accounts, held by wealthy Spaniards, could hold a total of around 6.0 billion euros (7.4 billion dollars), the business daily Expansion said in its online edition.

Spain received details of the accounts from French authorities, the paper said, quoting “sources close to the case”.