Erasing your digital breadcrumbs takes more than a hitting the “delete” button. Thousands of deleted emails at the center of an ongoing controversy surrounding former U.S. Secretary of State Hillary Clinton may still be retrievable, said Platte River Networks, the Denver Internet company that managed Clinton’s private server.

A spokesman for the company said in an interview with the Washington Post Saturday there’s no evidence the server hosting the Democratic presidential hopeful's emails was ever wiped. Wiping a server, a process that involves overwriting the original information with gibberish, is the only way to ensure the permanent deletion of data. But the company said it looks as if that never happened.

“Platte River has no knowledge of the server being wiped,” a company spokesman told the Post. “All the information we have is that the server wasn’t wiped.”

Clinton has said she and her team deleted some 31,000 email messages that were deemed personal and did not contain official business. But simply deleting messages from an inbox does not guarantee the information is gone for good.

The ongoing controversy over Clinton’s use of a private email server to conduct State Department business has dogged her 2016 presidential bid, with the Democratic candidate constantly forced to comment on the issue in interviews with the press. Earlier this week, Clinton apologized during an interview with ABC News, calling her use of the server a “mistake.”

“I’m trying to be as transparent as I possibly can,” Clinton told ABC.

In the meantime, some polls show Clinton, once considered the inevitable Democratic nominee, losing ground to her biggest rival, Sen. Bernie Sanders, Ind-Vt., who overtook Clinton in the most recent Quinnipiac poll in Iowa.

Clinton supporters have insisted the email debacle is a manufactured scandal concocted by her opponents. In a court filing earlier this week, the Justice Department said government officials have the authority to delete emails at their discretion. The brief received little attention until it was picked up by news outlets including the Washington Times and BuzzFeed.