Asahi Group Holdings revealed for the first time that cyberattackers employed ransomware to bring its domestic factories to a standstill, shedding more light on an online breach that’s raised questions about the country’s cybersecurity preparedness.

The maker of Japan’s most popular beer warned that the perpetrators may have made off with data, though it’s investigating the extent of the infiltration. Asahi has succeeded in isolating the system they attacked, and begun taking orders and commenced some shipments manually, it said in a statement. But it couldn’t gauge when full operations will resume.

The attack on Asahi this week has dominated headlines in Japan and raised concerns retailers will soon run out of Super Dry — the country’s top seller. Seven & I Holdings warned customers of possible shortages. Convenience store chains Lawson and Family Mart, whose outlets are ubiquitous across the country, warned that Asahi products, including food, might become scarce starting Friday.