Vodafone has launched an investigation into possible tax irregularities at Spanish cablenet Ono prior to its acquisition by the British firm last spring.

El Pais reports that the inflated figures were based on the sale of international calling minutes, sold without the balance being subject to VAT. However, the turnover from the business was incorporated into the general accounts, improving the overall company income.

The operation was carried out by a team of four employees, who have been removed from their positions. The question is whether or not Ono’s senior management knew anything about their actions.

President Jose Maria Castilian; delegate minister Rosalia Portela and CFO Carlos Sagasta all left the company immediately after the purchase.

Vodafone’s €7.2 billion purchase of Ono was agreed in March, but the company remained unaware of the alleged fraud until shortly before the transaction completed in July.