The Norwegian aluminum producer was hit by a ransomware cyberattack in March that crippled its computers and production.
"The cyberattack that hit us on March 19 has affected our entire global organization, with Extruded Solutions having suffered the most significant operational challenges and financial losses," said Chief Executive Svein Richard Brandtzaeg, adding that the company has "robust" cyber insurance in place.
The company recently postponed the publication of its first-quarter report to June 5, from April 30, as a result of the attack, which impacted the availability of certain systems and data to produce the quarterly report.
The company's extruded solutions unit saw sales volumes fall to 333,000 metric tons in the first quarter from 362,000 tons in the same quarter last year. The company had planned for current quarter volumes somewhat below the same quarter last year before the cyberattack, which further reduced actual volumes.
Norsk Hydro added that it maintains its expectation for the global primary aluminum market to be in deficit for the full-year 2019, with continued macro uncertainty.