BRUSSELS, April 26 (Reuters) – The European Union has started surveillance of imports of aluminium as U.S. tariffs threaten a further surge of the metal coming into Europe, the EU official journal said on Thursday. The data collected on the quantity and value of incoming aluminium products will help the bloc determine whether it needs measures to limit imports. The European Commission began an investigation last month to assess the need for potential “safeguard” measures for steel. The United States imposed import tariffs of 25 percent on steel and 10 percent on aluminium in March, although the European Union and six other countries secured temporary exemptions.