Twitter is reportedly being investigated in Ireland over alleged tracking of users through its special shortened links.

According to Fortune, one privacy expert suspected that Twitter “gets more information when people click on t.co links, and that it might use them to track those people as they surf the web, by leaving cookies in their browsers,” and so requested further details from Twitter, which the company rejected on the grounds that it would be too much effort to compile the information.

In response, the man “complained to the Irish Data Protection Commission (DPC), which on Thursday told him it was opening an investigation.”

“The DPC has initiated a formal statutory inquiry in respect of your complaint,” declared the DPC to the privacy expert. “The inquiry will examine whether or not Twitter has discharged its obligations in connection with the subject matter of your complaint and determine whether or not any provisions of the GDPR or the [Irish Data Protection] Act have been contravened by Twitter in this respect.”

Twitter’s European headquarters are located in Dublin, Ireland, which has been seen by Big Tech companies, including Google, Facebook, and Apple, as a tax loophole haven for many years.

In 2016, the European Commission accused Ireland of giving Apple “illegal tax benefits” worth “up to €13 billion.”