Last week, European Union antitrust regulators ordered Apple to pay up to 13 billion euros ($14.5 billion) in taxes to the Irish government after ruling that Ireland granted undue and selective tax benefit to the company.

Apple denies that Dublin gave it any tax breaks, a view shared by Ireland's Office of the Revenue Commissioners, which assesses and collects taxes, and the Irish government, which on Friday agreed to join Apple in appealing the decision.

The Commission is now actively scrutinising multiple tax opinions given to multinationals in Ireland and focusing on around six that could lead to Apple-style investigations, the Sunday Business Post said, without quoting any sources.

Irish Finance Minister Michael Noonan has, along with the Revenue Commissioners, said the opinions given to Apple were done in accordance with the law of the time and that any other company could and would have received the same advice. No companies received preferential treatment, they said.

The Commission has two outstanding cases involving two more U.S. firms, Amazon and McDonald's, both in Luxembourg, and is expected to press on with a crack down on other similar deals, officials and experts said last week.

(Reporting by Padraic Halpin; Editing by Raissa Kasolowsky)