OSLO (Reuters) - Norsk Hydro, one of the world’s largest aluminum makers, will postpone its first-quarter earnings report by more than a month as it struggles to recover from a March cyber attack, the company said on Friday. Hydro now aims to publish its results on June 5, five weeks later than planned, as it tries to gain access to administrative systems for reporting, billing and invoicing that were blocked by hackers demanding a ransom. “The revised date is conditional upon the planned timeline for restoring operational and reporting systems,” Hydro said in a statement. The company was forced to halt some production on March 19 and switch other units to manual operation after hackers blocked its systems. In terms of production output, most operations are back to normal or near normal levels following the attack, with Extruded Solutions, the most affected segment running at 85-90 percent capacity, the company said. While Hydro’s Primary Metal and Rolled Products business segments were running as normal, they still require a higher degree of manual operation, it added.