PITTSBURGH -- It's not exactly the Steel Curtain, but it's close enough.

The Pittsburgh Steelers upped their spy-prevention game for this year's practices by building a giant wall structure to cover one of their three fields.

Four black pillars about two stories high face an adjacent office building on Pittsburgh's south side, and for practice sessions the team can raise an attached giant black tarp.

The Pittsburgh Steelers built a structure where a two-story tarp can be raised to block the view of a practice field from adjacent buildings. Jeremy Fowler / ESPN

Coach Mike Tomlin playfully addressed the sudden quest for privacy during his news conference Thursday.

"I'll leave that somewhat mystical for you guys to hypothesize about the origins of that and its use, and at some point we'll address it the right way," said a smiling Tomlin, whose Steelers play the Tennessee Titans on Saturday in Heinz Field. "I know how it is, man. This is interesting times, drones and so forth. We do what we've got to do to prepare and get ready to play to have a level and fair competitive playing field."

Asked if he ever wonders who's watching from the office buildings in plain sight (which includes an FBI branch), Tomlin said, "I wonder about a lot of things. Some of the questions I get in here, I wonder about."

Tomlin isn't alone. Tight end Jesse James said he once saw a drone over the river during a practice, which he found "kind of sneaky" but had no idea whether other NFL teams were involved.

"You always have dudes out in the parking lot, and you don't know really where they are from and they send security out," James said. "It's not something you really notice while you're practicing, but if the defense is out on the field going against the scout team, you can see stuff going on."

The team's complex is situated between the Monongahela River and East Carson Street, which is fairly commercialized.

Steelers practices are open to local media covering the team every day, but reporting on happenings is prohibited unless a player confirms a specific action. The facility, which the team shares with the University of Pittsburgh football team, includes at least four fields.