NSA headquarters in Fort Meade, Md. National Security Agency The National Security Agency (NSA) has on occasion accidentally intercepted the private emails and phone calls of innocent Americans with no links to terrorism, two former U.S. intelligence officials told NBC News.

Some of the emails and phone calls were obtained via the NSA’s massive surveillance program that provides intelligence officials access to millions of Americans personal information. Following a bombshell report from the Guardian newspaper, the Obama administration was forced to admit the existence of the secret data mining program.

Ret. Adm. Dennis Blair, who served as President Obama’s director of national intelligence in 2009 and 2010, said in one particular instance, analysts mistakenly entered “one digit wrong” when collecting data on phone numbers and mined a significant amount of information on Americans with no terror ties.

After such a mistake, Justice Department officials reportedly had to report the errors to a secret national security court and destroy the data.

NBC News has more:

Another former senior official, who asked not to be identified, confirmed Blair’s recollection and said the incident created serious problems for the Justice Department, which represents the NSA before the federal judges on the secret court.

The judges “were really upset about this,” said the former official. As a result, Attorney General Eric Holder pledged to the judges that the intelligence agencies would take steps to correct the problem as a condition of renewing the NSA’s surveillance program.

The Justice Department publicly confirmed to the New York Times in April 2009 that Holder had taken “comprehensive steps” to correct a problem in NSA collection after it “detected issues that raised concerns.” But department officials declined to discuss details about what was described at the time as the “over-collection” of information.

It is unclear how many times the NSA has been forced to report improper collection of data to the secret court, but Blair indicated it happened more than one time.

This development could also explain why James Clapper, the director of national intelligence, told Congress that the NSA does not “wittingly” collect any data on American citizens.

Blair argued that the NSA would store the monumental amount of phone call information as a part of its agreement with telecommunications companies, however, officials could only “collect” the data after going back to the court to get permission. Some argue storing the data is the same thing as “collecting” it.