European officials have demanded that Luxembourg hand over documents relating to Amazon’s tax affairs as the online retail company becomes embroiled in a crackdown that has drawn in Apple, Starbucks and Fiat’s financial arm.

The EU’s competition commission has sent a request for information to the Grand Duchy, where Amazon’s main European operating company is based, about whether its decisions on corporate tax complied with state aid rules, two people familiar with the matter said.

“We are looking into what kind of arrangement Luxembourg has with Amazon,” said an EU official. Brussels is conducting fact-finding missions in a number of EU countries, another official said, as part of its drive to clamp down on “sweetheart” tax deals with large companies.