Sony has hired outside investigators to help clean its networks and apprehend those responsible for a massive breach that exposed the personal data of more than 100 million video game users.

The Japanese electronics company has retained a team from privately held Data Forte that is headed up by a special agent with the U.S. Naval Criminal Investigative Service to work alongside the FBI agents, who are also investigating the matter.

Sony said on Tuesday that it is also consulting with cyber-security detectives from Guidance Software and consultants from Robert Half International Inc’s subsidiary Protiviti to help with the clean-up.

Officials with Sony and the three firms did not respond to requests for information about the investigation. Agents with the U.S. Federal Bureau of Investigation have said little about the matter, except that they are looking into the breach of data, which might include some credit card numbers.

Connecticut Senator Richard Blumenthal, in a letter to Sony on Tuesday, asked the company to clarify the number of compromised credit card accounts and requested a detailed timeline outlining what the company knew about what was stolen and when it was known.

Blumenthal said he would ask U.S. Attorney General Eric Holder to investigate the matter and check whether Sony’s subsequent handling of the breach would make it civilly or criminally liable.

“I would appreciate a direct and public answer detailing what the company will do in the future to protect its consumers against breaches of their personal and financial information,” Blumenthal wrote.

“It’s a significant operation,” said David Baker, vice president of services with electronic security firm IOActive, which is not involved in the investigation.

He said that card issuers Mastercard and Visa Inc had likely appointed a firm to investigate.

Sony also said that it hired the law firm Baker & McKenzie to help it with the investigation.