Exchange operator Nasdaq OMX Group Inc found suspicious files on its U.S. computer servers and determined one of its Internet-based client applications was potentially affected by hackers, the Nasdaq Stock Market's parent company said on Saturday.

It said there was no evidence that hackers accessed or acquired customer information, or that any of its many trading platforms were compromised.

The FBI and outside forensic firms helped conduct the investigation, though Nasdaq OMX did not say when it was launched or when the suspicious files were found. The files, found in a Web application called Directors Desk, have been removed, the company said.

The probe is continuing, and securities regulators have been informed, a spokesman said by e-mail.

We continue to evaluate and enhance our advanced security controls to respond to the ever increasing global cyber threat and continue to devote extensive resources to further secure our systems, Chief Financial Officer Adena Friedman and Vince Palmiere, the VP of investor relations, said in a statement.

Cyber attacks against corporations and government occur constantly, they added.

The computer hacking was first reported late Friday by the Wall Street Journal.

On Saturday, Nasdaq OMX said it had been waiting until at the earliest February 14 before telling its customers, based on a U.S. Justice Department request, to facilitate the investigation.

(Reporting by Jonathan Spicer; editing by Mohammad Zargham)