Navistar International Corp. (NYSE: NAV) told the Securities and Exchange Commission on Monday that it was hit by a cyberattack in late May. 

The Lisle, Illinois-based truck and bus manufacturer said it is “minimizing potential impact” by working with third-party cybersecurity experts and federal law enforcement.

Navistar provided brief details in an 8-K SEC filing, saying it received a claim on May 31 that certain data had been extracted from the company’s IT system. 

A Navistar spokeswoman declined to say whether the company received a ransom demand or paid one.

“Following our incident response protocols, we immediately launched an investigation and deployed a series of countermeasures to protect our systems,” the company said in a statement. “The investigation is ongoing and we have taken proactive steps to help minimize the potential impact.”

Navistar is finalizing a merger through which it will become a subsidiary of Volkswagen AG’s TRATON Group following a March shareholder vote approving a $3.7 billion merger.

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