OWINGS MILLS, Md. -- The Baltimore Ravens' training camp has been closed to the public because of a $45 million construction project at the team's Under Armour Performance Center.

The only people who can see camp this year are team officials, reporters and the construction workers who've been hired to build a two-story expansion that overlooks the practice fields.

Ravens coach John Harbaugh joked that the team isn't taking any chances that its plays, formations and trick plays will make their way to their AFC North rivals.

"I just want to assure our fans and everybody else that all of the contraction workers have been fully vetted," Harbaugh said. "None of them are from Cincinnati or Pittsburgh. We checked them all out."

The Ravens practice in the early mornings, when the construction workers are scaling the roof and pouring concrete. Some workers are wearing Ravens hard hats.

Like many NFL teams, the Ravens are particular about what the media can shoot on camera or report during practice. And, with how the offseason has gone for Baltimore -- from the injuries to the retirements -- it might be in the team's best interest to play it safe.

"We have a construction ban on any worker traveling from Cincinnati or Pittsburgh here to work on our facility during training-camp practices," Harbaugh said. "There's your scoop."