In a statement, the PJ said that the detainees, who worked in different sectors, are also suspected of crimes of criminal association, money laundering and document forgery.

The detention of the seven men and four women, aged between 25 and 55 years, took place in the course of the searches of some 40 residential and non-residential premises in the municipalities of Paços de Ferreira, Paredes, Porto, Vila Nova de Gaia, Santo Tirso, Guimarães, Maia, Marco de Canaveses and Felgueiras.

According to what has been determined so far, the presumed leader of the criminal association, the owner of an accounting company, in collusion with third parties, engaged in in 2016 and 2017 in a repeated and constant practice of behaviour to obtain undue tax benefits for his customers, notably in refunds of value-added tax and in the artificial reduction of taxable income for the purposes of corporate tax, thus reaping benefits to which they knew they were not entitled.

To this end, the PJ state, false data were declared to the tax authority, with invoices issued for purchases and services provided in the name of taxable persons whose accounts the company managed.

"They have produced false documents, including employment contracts, income statements, salary receipts, registration or maintenance of workers in companies, tax and social security returns and others, in order to obtain for third parties advantages granted by the state and the approval of loans from financial institutions, as well as the granting of support under [European Union] funding programmes, namely Portugal 2020," the PJ said.

According to the PJ, in this way this "criminal association" and the group of companies involved denied the state some €2 million in relation to VAT and corporate tax.

The police operation involved some 120 officers, including judicial magistrates and prosecutors, investigators from the PJ’s northern directorate and the departments of Braga and Aveiro, and tax inspectors from Porto.

During the operation, several vehicles, computer equipment, mobile phones, accounting and fiscal documentation were seized to secure evidence, the PJ said.

The detainees are to be brought before a court to be questioned by a judge, who is to decide on any restrictions on their movements.