Steelmaker Nucor said on Wednesday that it had experienced a cybersecurity incident and temporarily shut down some of its production operations as a precaution.

The North Carolina-based company said it discovered "unauthorized third party access to certain information technology systems" that it uses.

Nucor did not specify which production operations had been "temporarily and proactively" shut down in a regulatory filing but said it was currently working on getting them back up and running. 

Its facilities are primarily scattered across North America. 

The steelmaker’s response to the cybersecurity incident involved "taking potentially affected systems offline" and carrying out other steps, according to the filing.  

"The company is actively investigating the incident with the assistance of leading external cybersecurity experts and has notified federal law enforcement authorities," Nucor said in the Securities and Exchange Commission filing. "As the investigation of the incident is ongoing, the company will continue to monitor the timing and materiality of the incident." 

Nucor considers itself the "largest and most diversified steel and steel products producer" in North America. It makes a number of products such as bars, beams, electrical conduit, girders and fasteners, according to its website.