Washington (CNN) A former top counterintelligence expert at the FBI, now at the center of a political uproar for exchanging private messages that appeared to mock President Donald Trump, changed a key phrase in former FBI Director James Comey's description of how former secretary of state Hillary Clinton handled classified information, according to US officials familiar with the matter.

Electronic records show Peter Strzok, who led the investigation of Hillary Clinton's private email server as the No. 2 official in the counterintelligence division, changed Comey's earlier draft language describing Clinton's actions as "grossly negligent" to "extremely careless," the sources said.

The drafting process was a team effort, CNN is told, with a handful of people reviewing the language as edits were made, according to another US official familiar with the matter.

The shift from "grossly negligent" to "extremely careless," which may appear pedestrian at first glance, reflected a decision by the FBI that could have had potentially significant legal implications, as the federal law governing the mishandling of classified material establishes criminal penalties for "gross negligence."

Senate Judiciary Chairman Chuck Grassley, R-Iowa, raised questions over why the change was made after receiving documents from the FBI last month, but the identity of who was behind the edit has not been reported until now.

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