Singer and actress Jennifer Lopez slipped into the Hart Senate Office Building on Wednesday afternoon for a mysterious meeting inside presumptive Democratic nominee Sen. Barack Obama’s (Ill.) office.

The Hollywood star, sporting a black cocktail dress and carrying an orange handbag, surprised staffers when she was spotted walking through the Hart atrium and taking the elevator to Obama’s seventh-floor office.

When asked what brought her to the Hill, Lopez smiled.

“I’m not ready to do any press yet,” she said, her eyes hidden behind a pair of big, black sunglasses.

Word spread fast of Lopez’s presence, and a herd of staffers and tourists — thinking they were waiting to see Obama — amassed, their cell phone cameras at the ready. As it happens, Obama was scheduled to be in St. Louis, Mo., today at the Barnes-Jewish Hospital.

Rumors circulated that Lopez may be writing Obama a song.

As the throng continued to gather, Sens. Arlen Specter (R-Pa.) and Bill Nelson (D-Fla.) walked by with little fanfare, and Sen. Jeff Bingaman (D-N.M.) stopped short of walking into a photo visitors were taking by the nameplate outside Obama’s door.

The security detail guarding Obama’s door grew from two to four as Lopez’s meeting continued. After an hour and a half passed, an Obama staffer came out to break the bad news.

“She’s gone,” he said, explaining that she left even more secretively than she entered.