White House Press Secretary Josh Earnest resumes his press briefing following a brief evacuation of the Press Briefing Room at the White House June 9, 2015 in Washington, DC.National Journal

In the middle of Tuesday's White House briefing, Secret Service officers abruptly interrupted the proceedings and evacuated the briefing room.

Later it was discovered that it was a bomb threat, called into the Metropolitan Police Department, who alerted the Secret Service. With the White House in sight, the press corps, including this reporter, waited next door at the Old Executive Office Building, until we were allowed back in about a half-hour later. But when the journalists returned to the James S. Brady Press Briefing Room, they found that the TV cameras for CNN, ABC, and others had all been covered or turned toward the ground.

The press corps' indignation was made clear instantly with a question from ABC's Jonathan Karl. "Josh, before the alarm, who covered up the cameras in this room?" Karl asked, unnerved. "Somebody cut off our ability to see what was going on in this room by turning the cameras down. Who did that and why?"

Press Secretary Josh Earnest didn't have much of an answer, only saying that he'd been evacuated from the briefing room alongside the rest of us. During Wednesday's briefing, when Karl followed up, Earnest punted to the Secret Service.

Though Mike Roche, a former Secret Service agent, was never assigned to the White House, he said he could surmise that officials obstructed the cameras "to not disclose bomb-detection techniques—i.e., dogs or electronic sniffers and jammers. ... They would not want their methods disclosed to a potential national audience."

Speaking on background, a federal law-enforcement official echoed that sentiment, explaining that "the Secret Service typically does not allow filming of these sweeps."

Christi Parsons, the president of the White House Correspondents' Association, was set to meet with Earnest after the briefing to discuss the situation. "The WHCA board is talking with several people involved in the incident—members of the press corps who were evacuated and whose offices were searched, camera crews whose equipment was repositioned, administration officials who were in the West Wing at the time."

"Whenever a government agent puts his or her hands on a journalist's equipment, it alarms us," she said. "Right now, the WHCA board is trying to figure out precisely what happened and to determine the right response."

On a practical level, covering up the cameras can be seen as just plain tampering with equipment owned by news organizations. When they bring in "millions of dollars of equipment, as media we're a little bit sensitive about having it moved, maneuvered, adjusted," said Charles Bierbauer, a former CNN White House correspondent and former WHCA president who's now the dean of the College of Information and Communications at the University of South Carolina.

But Karl and Parsons's rancor airs publicly a long-running tension between the press corps and White House press officials.

For the press, it was an infringement on the little authority they have.

The briefing room and press quarters at the White House are notoriously cramped, and the press corps and WHCA zealously protect what access and space they enjoy. What White House reporters do have is the freedom to document what happens in the briefing room with notebooks, smartphones, iPads—and TV cameras. The room is considered hallowed ground for the press corps, the one place in the mansion they can ask questions and get—albeit opaque and roundabout—answers.

"The White House has control of most of the situation: Where you go, what you see," Bierbauer said. "The media don't have control of a whole lot."

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