The U.S. Justice Department has opened an investigation into allegations that International Business Machines abused its dominance of the mainframe business, said Computer and Communications Industry Association chairman Ed Black.

The CCIA had urged the Justice Department to open the probe, accusing IBM of anti-competitive conduct for doing things like refusing to license its mainframe operating systems to users of Hercules for installation on machines other than IBM mainframes.

Hercules is an open-source project that would allow IBM's mainframe operating systems to run on Intel-based and Advanced Micro Devices-based computers.

We are aware that Justice has begun the CID investigatory process, said Black. A CID is the equivalent of a subpoena and indicates that an investigation is under way. The scope is quite broad, said Black.

Neither IBM nor the Justice Department could immediately be reached for comment.

The CCIA also accused IBM of withdrawing licenses for its operating systems from customers who use non-IBM hardware, retaliating against business partners that also support migration as an option for customers, tying its mainframe operating systems and hardware and acquiring mainframe startup PSI to stifle competition.

Black said the decision reflected a pledge by the Obama administration that they're going to take antitrust seriously. They mean it.

The move is similar to other probes of dominant firms that the Justice Department has opened.

The head of the Justice Department's antitrust division, Christine Varney, said in early May that she planned to take a more aggressive approach with dominant firms that use their market power to crush competition.

The department is also investigating telecommunications companies for potential antitrust violations. Smaller telecommunications firms have long complained that the giants -- AT&T and Verizon Communications -- used their market share to squeeze out smaller rivals.

The smaller companies have also protested against the exclusive deals that cell phone companies made with handset makers, among other issues.

They're (the Justice Department) going to want to make this stick, said antitrust attorney David Balto. There's good reason for IBM to be concerned.

(Reporting by Diane Bartz; Editing by Gary Hill)