Fairfax County public schools could owe more than $6 million to the federal government after mistakenly destroying several thousand employee files that noted citizenship status.

School officials said that about 5,600 employees’ files were shredded in 2006 but that the discovery was made only last year, after the administration audited hiring records.

A similar search also conducted last year found that the school system had hired seven felons, including a special education teacher who was convicted of helping to smuggle heroin into the country. It is against Virginia law for schools to hire felons.

The files are known as I-9 forms and are completed by applicants as part of the pre-employment process to verify a person’s identity and eligibility to work in the United States. Employers are supposed to keep the files for at least three years after a person is hired or for one year after the employee leaves, whichever is longer.

Employers who don’t keep the documents for inspection can face fines ranging from $110 to $1,100 per form, according to officials with Immigration and Customs Enforcement.

“ICE is committed to protecting employment opportunities for the nation’s lawful workforce and targeting businesses that knowingly employ unauthorized workers,” said Brandon Montgomery, a spokesman for ICE. “If employers are not in compliance with the law, and an I-9 inspection of their business is conducted, it may result in civil fines and lay the groundwork for criminal prosecution.”

ICE officials said they had no record of being contacted by Fairfax County Public Schools regarding the destroyed files. Fairfax schools officials confirmed that they had not notified ICE about the mistake.

ICE officials did not say if they are looking into levying fines. If assessed the maximum penalty for each form, the school system could owe the federal government $6,160,000.

The agency considers several factors in determining possible penalties, ICE officials said, including “the size of the business, good faith effort to comply, seriousness of violation, whether the violation involved unauthorized workers, and history of previous violations.”

Representatives from Fairfax teachers organizations questioned the administration’s handling of the sensitive documents, which include an employee’s home address, date of birth and Social Security number.

Kimberly Adams, president of the Fairfax Education Association, which has 5,000 members, said she was concerned that the Human Resources Department “could fail so miserably.”

“We worry about what else is missing,” Adams said. “It is disheartening that it took until now for our system to enforce a policy of internal document review and control. It is stunning what can be found when the microscope is applied.”

Fairfax officials said that employees were told of the error in December. About 3,800 have filled out new I-9 forms.

“Completed I-9 forms are now scanned into our database and have been since 2006,” Fairfax Schools officials wrote in a statement to The Washington Post. “The electronic copy ensures retention and provides the most secure means of safeguarding the records.”

Steven Greenburg, president of the Fairfax County Federation of Teachers, which represents 4,500 employees, said that Superintendent Karen Garza and Phyllis Pajardo, assistant superintendent for human resources, apologized profusely to school staff.

Greenburg said the sensitive documents were shredded, which is better, he said, than their whereabouts being unknown.

“But they shouldn’t have been shredded to begin with,” he said.