(CNN) -- The Defense Department will reopen its investigation into employees who are alleged to have downloaded child pornography, a spokesman said Wednesday.

The Pentagon's Defense Criminal Investigative Service will review 264 cases, according to spokesman Gary Comerford. The department had stopped the reviews because of a lack of resources, he said.

Some of the cases may be referred to military criminal investigations, while cases where it appears a criminal investigation cannot be done will be sent to Defense Department leadership for consideration.

The incidents were part of Project Flicker, a nationwide child pornography sting conducted several years ago by Immigration and Customs Enforcement agents. The Department of Defense released documents pertaining to the sting earlier this summer.

A Yahoo News investigation found that the department followed up on only a fifth of the cases after federal investigators informed it of employee involvement.

"I have tasked Defense Criminal Investigative Service representatives with reviewing each and every Project Flicker and related referral DCIS received so as to ensure action was taken regarding these allegations involving employees of the Department of Defense," James Burch, deputy inspector general for investigations, said in a statement released Wednesday.

Among the employees identified in a series of reports released by the department were some listed as having security clearances at the top secret level or higher. They worked for groups within the department such as the National Security Agency and the National Reconnaissance Office, two of the country's top intelligence agencies.

Some of the employees are suspected of having used their work computers to view pornographic websites.

Some employees involved in the investigation have pleaded guilty to charges of child pornography, but other inquiries were dropped or are still open. One case against a Defense Department contractor who allegedly admitted to having viewed pornographic material of children was dropped "due to a lack of resources," according to one of the reports from 2009.