As many as 390,000 current and former Homeland Security Department employees, contractors and job applicants may have had their private data compromised in a newly disclosed computer hack discovered last year.

DHS spokesman S.Y. Lee said internal notices about the data breach discovered in September at KeyPoint Government Solutions Inc. were sent to employees starting April 27. The KeyPoint hack is separate from the hacks of the Office of Personnel Management attacks disclosed earlier this month.

Notifications have taken longer for those outside the department. In a letter to one former job applicant dated June 5, the government advised that the data breach was "initially discovered in September." A copy of the letter was obtained by The Associated Press.

KeyPoint officials did not immediately respond to emailed requests for comment Monday.

Lee said the hack is a separate breach than one involving the same government contractor that was disclosed by the government in December.

The OPM acknowledged then that computer files of more than 48,000 government workers, including about 25,000 from DHS, may have been compromised.

The latest disclosure comes amid an ongoing investigation of a massive hack of government files held by OPM. The records of as many as 14 million current and former civilian government employees may have been compromised.