BUTLER, PA – At least five U.S. Secret Service officials involved in planning Donald Trump’s July 13 rally in Butler, Pennsylvania, where a gunman attempted to kill the former president, have been placed on leave, according to two sources familiar with the situation.

The officers are still on duty but are not allowed to participate in any operational tasks, including security planning, the sources told ABC News.

The Secret Service’s Office of Professional Responsibility is intensifying its investigation. While the investigation prior to Butler focused on omissions, errors and planning, a number of other issues are now in focus, including the number of classified threats made by Iran against former President Trump and the agency’s security policy actions in light of the new intelligence information.

An official told ABC News that this means there may be more senior officials involved in the review.

“The U.S. Secret Service is committed to investigating the decisions and actions of personnel related to the event in Butler, Pennsylvania, and the attempted assassination of former President Donald Trump,” the agency said. “The U.S. Secret Service’s mission security review is progressing and we are investigating the processes, procedures, and factors that led to this operational failure.”

The agency said it expects the “highest professional standards” from its staff and declined to comment further.

Trump was struck in the ear by a bullet in the attack at his July 13 campaign rally, which also killed a bystander and injured two others, officials said. The gunman, identified by the FBI as 20-year-old Thomas Matthew Crooks, was killed by Secret Service agents.

Multiple sources told ABC News that the U.S. Secret Service recently made arrangements to allow Trump to resume outdoor campaign rallies by surrounding his lectern with bulletproof glass.

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