Apple may be in breach of the European Union’s new digital competition rules in how its app store operates, the European Commission said following a new investigation.

The commission said its preliminary view is that Apple is “violating” the Digital Markets Act regarding its app store rules by preventing developers from sending consumers to alternative ways to pay or download content outside of Apple’s ecosystem.

“Our preliminary position is that Apple does not fully allow this,” EU competition chief Margrethe Vestager said in an emailed statement.

Apple can defend itself in writing until the European Union regulator makes a final decision by March 25 that the company has broken the rules. It could then be fined up to 10% of its global revenue.

The Commission also opened a new research non-compliance regarding the fees charged by Apple to the programmers for user downloads.

Apple “is confident that our plan complies with the law and estimates that more than 99% of developers would pay the same or less fees to Apple under the new business terms we have created,” company spokesman Julien Trosdorf said.

Apple is the first major tech company the commission has called out for violating the DMA’s strict rules designed to make it easier for smaller players — companies that rely on app stores and search engines — to win customers.