(Reuters) -Top U.S. oilfield services firm Halliburton said on Friday it was working with law enforcement to determine the extent of a computer systems breach and was yet to determine if the incident would have a material impact on its business.

The $23-billion company became aware of the cyber attack on Wednesday, it said in its first securities filing about the breach, adding its "ongoing investigation and response included restoration of its systems and assessment of materiality."

The company also said it had taken certain systems offline to protect them.

A spokesperson declined to comment on whether the company had been contacted by the people behind the breach.

Reuters was the first to report about the cyber attack on Wednesday.

The attack appeared to impact business operations at the company's north Houston campus as well as some global connectivity networks, a person familiar with the matter said.

The company had also asked some staff not to connect to internal networks, the source said.

The U.S. Department of Energy said on Thursday the Halliburton cyber incident had not impacted any energy services.

(Reporting by Seher Dareen in Bengaluru; Editing by Savio D'Souza and Shreya Biswas)