The House Oversight and Government Reform Committee on Wednesday grilled Office of Personnel Management (OPM) Director Katherine Archuleta over the massive hack of personal information of up to 18 million federal employees, Slate reported.

The head of the agency, which keeps up to 780 separate pieces of information on those individuals, however, put the number of affected current and former employees at 4.2 million, according to NPR; higher figures refer to "a preliminary, unverified, and approximate number of unique Social Security numbers ... I am not comfortable with," Archuleta insisted.

Committee Chairman Jason Chaffetz, a Republican from Utah, urged Archuleta to resign, telling the OPM chief that "I think you're part of the problem." The agency and Archuleta last week had already come under fire from the American Federation of Government Employees (AFGE), whose president, David Cox, had criticized the handling of the data breach in a strongly worded letter, Fox News recalled.

"Based on the sketchy information OPM has provided, we believe that the Central Personnel Data File was the targeted database, and that the hackers are now in possession of all personnel data for every federal employee, every federal retiree, and up to one million former federal employees," Cox had written.

The AFGE president said that other information stolen from the OPM database may include workers' age, gender and race details; addresses; dates of birth; employment and pay history; health insurance, life insurance and retirement data; and military records and veterans status.

The League of United Latin American Citizens (LULAC), however, defended Archuleta against what the District of Columbia-based Hispanic civil-rights group called attempts to "scapegoat" the OPM director.

"We are confident that the Congressional inquiries will conclude that Director Archuleta was not responsible for the breach and that she is uniquely qualified to develop systemic long term solutions that will ensure U.S. systems are protected from cyber attacks," LULAC National Executive Director Brent Wilkes said in a statement.

The organization pointed out as the first Latina to lead the Office of Personnel Management, Archuleta was a key appointment since the agency is "responsible for securing a talented and diverse federal workforce."