The Spanish police raided the Madrid subsidiary of one of China’s largest banks on Wednesday and arrested five of its directors as part of a broad investigation into money laundering.

The Madrid branch of the Industrial and Commercial Bank of China is accused of helping several Chinese and Spanish criminal syndicates commit financial fraud, according to Europol, the police agency of the European Union, which helped the Spanish police in its investigation.

The investigation, code-named Operation Shadow, builds off a case last year by the Spanish police that claimed that a group had laundered 40 million euros of earnings from discount stores operated by Chinese businessmen across Spain. The group was also accused of importing goods from China without declaring them to Spanish customs authorities, avoiding the payment of import and tax duties. Thirty people were arrested in that case.

After last year’s operation, the Spanish police said they followed “the money trail” and found that the syndicate had deposited its earnings at the Spanish subsidiary of ICBC. The bank then sent it to China “without checking their origin as required by law,” according to Europol.