Adds disclosure in paragraph 4, background on Q1 earnings in paragraph 5

May 14 (Reuters) - Steelmaker Nucor NUE.N said on Wednesday it had halted certain production at various locations after identifying a cyber security incident that involved unauthorized third-party access to certain information technology systems it used.

The Charlotte, North Carolina-based company said it is in the process of restarting the affected operations as it investigates the incident along with external cyber security experts.

Nucor has notified federal law enforcement authorities and is taking the potentially affected systems offline, while also implementing other containment, remediation or recovery measures, it said in an SEC filing.

The company did not immediately respond to Reuters' request for further details on the incident.

Nucor last month beat analysts' estimates for first-quarter revenue and profit, helped by higher steel shipments and improving steel spot prices.

(Reporting by Aatreyee Dasgupta in Bengaluru; Editing by Shreya Biswas)

((Aatreyee.Dasgupta@thomsonreuters.com;))