The .eu watchdog said it is investigating evidence of further breaches of its registration rules since the launch of the top level domain (TLD) in April.
After confiscating over 70,000 Cyprus-based domain names last month, EURid said it is "looking into" relatively high numbers of registrations in other European countries such as Malta and Luxembourg.
Analysts say this could indicate registrars have set up phantom businesses in these countries to 'warehouse' domain names and sell them on at a profit, which would break EURid rules.
"We are looking into anything that looks strange," said the group's spokesperson Patrik Linden. "It might just be someone with a lot of domain names but we have a team studying it."
A report by internet monitoring group Ipwalk published earlier this week showed that Malta holds the most .eu domain names per citizen in Europe.
It also has many more .eu registrations than those of generic top-level domain names such as .com and .net, which have been available for a longer period of time.
Ipwalk said this could suggest that many more .eu domain names are being stockpiled by registrars in breach of EURid's rules.
Last month, EURid suspended 74,000 domain names registered in Cyprus, saying it suspected that three companies — Ovidio Ltd., Fausto Ltd. and Gabino Ltd. — were being used by a syndicate of 400 registrars to warehouse domains.
It said it would continue to investigate abnormal patterns in registration activity.
"Hopefully, people will realise that these activities are not worth it, and that we will take action," said Linden. "We also want to make these domain names available again."
Linden added: "If a company or individual has purchased a large number of domains then that's ok. But if registrars are doing it then it isn't - that constitutes 'warehousing'."
He also explained that statistically, because of the small populations of Luxembourg and Malta, and the fact that a lot of companies choose to register companies in these territories, there could be a perfectly reasonable explanation for the high registration count.
Around 2.5m .eu domains have been registered in total, far outweighing the expectations of EURid of "perhaps 1m registrations in the first year". The UK is the second-largest country for .eu registrations, after Germany (followed by The Netherlands, France and Sweden).
For further reading on this and other domain issues, check out GoDaddy CEO and founder Bob Parsons' blog.