SAN FRANCISCO, Nov 15 (Reuters) - CME Group Inc, the world's largest futures exchange operator, said Friday one of its clearing systems was hacked in July, and the incident is the subject of a federal criminal investigation.

Certain customer information relating to CME ClearPort, which clears contracts mainly tied to energy, was compromised, CME said in a statement.

There is no evidence that trades were adversely impacted or that CME's other clearing services were disrupted, it said.

CME is cooperating with law enforcement in its investigation, the statement said.