Washington (CNN) A long-running Republican-led investigation into the handling of classified information on Hillary Clinton's private email server did not find any evidence that China had successfully hacked the former secretary of state, confirming the findings of the FBI , according to a memo released by two senior senators this week.

"Neither the committees nor the FBI were able to confirm whether an intrusion into the server occurred," Grassley and Johnson said in a news release Wednesday.

Concerns of an intrusion by China into the server were first raised by two officials from the Intelligence Community Inspector General's Office, which helped initiate the original review of Clinton's email practices as secretary of state that was later referred to the FBI, according to the memo. Both officials were interviewed by the Senate investigators as part of their probe.

One of the officials told Senate investigators that Peter Strzok , a senior FBI official on the Clinton investigation who was fired last year after the release of text messages he'd sent that were critical of Trump, was "aloof and dismissive" when presented with information about the potential Chinese hack.

The other Intelligence Community Inspector General's Office official told investigators that FBI employees were "poker faced" when shown the information, which concerned the appearance of a Gmail address that had a similar name to a Chinese trucking company in the metadata of a tranche of Clinton emails.

A letter in April to Grassley and Johnson from the inspectors general for the intelligence community and the Justice Department that's included in the memo says a computer specialist who administered one of the private email systems told the FBI that he had created the Gmail account to transfer archived emails between Clinton servers.

The FBI had been aware of the Gmail account in question before the two intelligence community inspector general officials expressed their concerns over it in the meeting with Strzok, the memo shows.

After its own investigation, the FBI concluded in 2016 that there was no "direct evidence" that the server had been successfully hacked, though former FBI Director James Comey conceded that "given the nature of the system and of the actors potentially involved, we assess that we would be unlikely to see such direct evidence."

Separately, the officials from the Intelligence Community Inspector General's Office also told Senate investigators that they had witnessed efforts by senior State Department officials to try to avoid labeling certain emails as classified as part of the review.

The Senate investigation into the Clinton server is continuing and has shifted its focus toward a classified appendix of a report from the Department of Justice Inspector General's Office scrutinizing the FBI's investigation that was released last year, according to the memo. Investigators are interested in the decision by the FBI to not seek access to "certain highly classified information potentially relevant to the investigation" and have written to the Justice Department with questions, they said in the memo.