The Guardia Civil in Spain is investigating dozens of complaints from the victims of the adultery website Ashley Madison, data hack who have said they are being extorted by blackmailers online for amounts ranging between €500 to €2000 (£367 to £1,470).

Ashley Madison and its sister sites operated by parent company Avid Life Media were targeted for one of the most high-profile hackings of recent years by the Impact Team. The group dumped the personal and financial data of more than 32 million users from 26 countries on the dark web.

According to the Spanish IT firm Tecnilogica there were 1.1 million users of Ashley Madison in Spain, the second highest number of users in a European country, behind Britain.

The Spanish national daily El Pais reported that in the wake of this summer's leak, dozens of Spanish users of the site have come forward to authorities saying they are being blackmailed by individuals who say they will give details of their use of the site to their families and loved ones. They appear to have selected their targets by collaborating their data with information on social media networks.

ASHLEY MADISON HACKED: Full coverage of the cheating website's fall from grace, including guides on how to check if someone's email address was on its database in our Flipboard magazine

Spanish investigators from the country's Central Operations Unit have determined that the blackmailers are operating from abroad. As such, the Guardia Civil is working in collaboration with other police forces in other countries to pinpoint the origins of the blackmailers.

The Federal Bureau of Investigation (FBI) and Canadian police forces joined the probe into the data breach in August during the immediate aftermath of the leak.

Three Canadian police forces – the Royal Canadian Mounted Police, the Ontario Provincial Police and the Toronto Police Services – began the initial investigation.

273,320 email address belonging to Canadian domains were released in the first data dump on the dark web on 19 August. In excess of 823,000 of the 9.6 million released credit card transactions were recorded as having a Canadian address. Avid Life Med is a Toronto-based company.