The FBI is stepping up its interviews regarding Hillary Clinton’s private emails during her time as Secretary of State, focusing on determining whether state aides sent classified material improperly, according to Politico. The website said it learned early last month the FBI asked for documents from a company that dealt with the Internet server arrangement after Clinton left her position in the federal government.

A former high-ranking State Department official was also interviewed by the FBI, which asked if department officials were worried whether email communication put classified information at risk. The official spoke to Politico on the condition of anonymity, and the FBI declined to comment about any ongoing efforts.

“This sounds to me like it’s more than a preliminary inquiry; it sounds like a full-blown investigation,” Tom Fuentes, a former FBI assistant director told Politico. “When you have this amount of resources going into it …. I think it’s at the investigative level.”

Clinton has tried to put the email scandal behind her amid her presidential campaign. Thousands of pages of Clinton’s emails have been released by the State Department.

The scandal came about over the summer after Clinton came under public scrutiny over how she used her private email account for government-related business while she was Secretary of State. She handed over the thumb drive and private server, and has said previously she should have used an email address for personal matters and a separate one for her work with the State Department.

The email issue has come up during her campaign, and even was a question during the first Democratic presidential debate last month. She said during the debate that she made a mistake, and her opponent Bernie Sanders came to her aid, saying the American people are tired of hearing about Clinton’s emails.