BRASILIA: Brazilian fuel distribution company Ultrapar Participações S.A. said on Monday that operations at some of its subsidiaries are fully operational again after being the target of a "ransomware" cyber attack.

In a securities filing, Ultrapar said that all security and control measures were taken and, as of Jan. 14, the operating systems of the company and its subsidiaries have been gradually restored.

Ultrapar had alerted the attack on Jan. 12 without giving details.

"Right now, 100% of the company's critical information systems and those of its subsidiaries are fully operational," it said in the filing.