By David Winning

SYDNEY -- Meatpacker JBS SA kept some Australian plants offline while others were operating at limited capacity on Wednesday, the country's agriculture minister said, as authorities strive to trace the origins of a ransomware attack on the company.

Processing of beef, lamb and pork in Australia was disrupted by the attack on JBS that also brought operations at several large U.S. meat plants to a halt, said David Littleproud, Australia's agriculture minister.

Brazil-based JBS, the world's biggest meat company by sales, is working with the Australian government on protocols that would allow more meat processing to restart, he said.

"That needs computer systems, obviously, to support that so that we can give confidence not only to the domestic market, but also to our international trading partners," Mr. Littleproud said.

Mr. Littleproud said Australian authorities are meeting with U.S. law-enforcement agencies to pinpoint the source of the attack. The Australian arm of JBS uses the same computer system as the company in the U.S., which is why operations in both countries were affected, he said.

On Tuesday, White House principal deputy press secretary Karine Jean-Pierre said JBS reported that the attack originated from a criminal group likely based in Russia.

"The White House is engaging directly with the Russian government on this matter and delivering the message that responsible states do not harbor ransomware criminals," Ms. Jean-Pierre said.

The disruption caused by the ransomware attack is the latest blow to Australia's meat industry after a prolonged drought reduced livestock numbers.

JBS accounts for roughly a quarter of Australia's red-meat processing, with several large plants located in the country's eastern states. Calls to the company's Australian headquarters weren't answered.

Mr. Littleproud said JBS ran limited operations in New South Wales and Victoria states on Wednesday, while the government was hopeful that plants in Queensland could be restored at some level on Thursday. Australia continues to export around 72% of its meat, with significant supplies currently available for the domestic market, he said.

"It's also important to understand it's not just JBS that's impacted by this, it goes right back to the farm gate and obviously they're working as hard as they can to make sure that there's continuity in that supply chain," said Mr. Littleproud.

Several thousand meatworkers have been temporarily stood down while JBS works to bring operations back to full capacity, said Matt Journeaux, an official at the Australasian Meat Industry Employees' Union.

"They have no idea when this is going to be rectified or if there is any end in sight," he said.

Write to David Winning at david.winning@wsj.com

(END) Dow Jones Newswires

06-02-21 0754ET