At least five US Secret Service agents have been placed on administrative leave following the attempt on Donald Trump's life in Pennsylvania, US media reports.
They include the head of the Pittsburgh field office that coordinated security with local police, three other agents in the same office, and a member of Trump's personal detail, according to the BBC's US news partner CBS.
Trump, the Republican presidential candidate, was injured in the right ear by a bullet fired from a roof by Thomas Crooks, 20, at a rally in Butler on 13 July.
His burst of gunfire killed one crowd member and injured two others before he was shot dead by a Secret Service sniper.
Anthony Guglielmi, a spokesman for the Secret Service, said its review of "this operational failure" was ongoing, adding that agents were held to "the highest professional standards" and any violations could result in disciplinary action.
Kimberly Cheatle resigned as the service's director shortly after facing members of Congress in a contentious hearing where she failed to provide specific answers about the attack and her agents' response.
She has since been replaced by Ronald Rowe as acting director.
The House of Representatives has formed a task force to investigate the operational failures that allowed Crooks to fire on the crowd.
Trump held an outdoor rally in North Carolina on Wednesday, his first since the assassination attempt. His podium surrounded by bulletproof glass.
BBC News has contacted the Secret Service for comment.
