The Department of Energy’s electronics network was attacked by hackers in mid-January but no classified data was compromised, the agency said in a letter to employees. The attack “resulted in the unauthorized disclosure of employee and contractor Personally Identifiable Information,” the Energy Department said in the letter, which was received by employees at its headquarters in Washington late on Friday and obtained by Reuters on Monday. The department said it was working with federal law enforcement to gather more information on the nature and scope of the attacks and assess the potential impact on staff and contractors. “Based on the findings of this investigation, no classified data was compromised,” the letter said. Government agencies are required to disclose details when confidential personal data has been hacked.