CARTAGENA, Colombia -- In the early hours of April 12, the booze flowed and a thumping techno rumba shook the walls at Tu Candela, a popular nightclub whose dance floor recalls the narrow confines of a wine cellar.

Dozens of couples gyrated to the pulsing sounds emanating from flat video screens throughout the club, which is in Cartagena’s walled-in colonial section. When the party ended around 4 a.m., two couples headed for the Hotel Caribe, an imposing castle-like structure facing the Caribbean, two miles from the club.

The couples’ encounter at one of Cartagena’s hottest nightspots set the stage for the still-unfolding prostitution scandal that’s snared 12 U.S. Secret Service agents and a dozen members of the U.S. armed forces.

The military personnel remain under investigation. Of the Secret Service agents, eight have resigned, retired or been fired and one has had his national security clearance revoked, making his dismissal almost certain. Three have been cleared of misconduct.

But the investigation is hardly over of a scandal that’s added a new issue to the presidential campaign and raised questions in Congress about whether contact with prostitutes by members of the advance team preparing for President Barack Obama’s attendance at the April 14-15 Summit of the Americas compromised Obama’s security.

U.S. investigators who’ve traveled to Cartagena to interview hotel chambermaids as well as taxi drivers who transported the women and the Secret Service are still trying to unravel events, according to hotel employees and drivers. One driver said that as recently as Monday a man who identified himself as a U.S. investigator had approached him with pictures of women who might have slept with agents at the Caribe.

Whether investigators have requested hotel video and copies of identification cards the women presented at the reception desk isn’t known. Ana Beatriz Angel, a Caribe spokeswoman, declined to discuss the matter. “The hotel will make no comment,” she said.

The Secret Service acknowledges that it’s checking whether its employees consorted with strippers and prostitutes in advance of Obama's visit last year to El Salvador.

The Colombia scandal erupted when Dania Suarez, 24, who was one of the two women dancing at Tu Candela, began knocking on hotel room doors, complaining that her date had refused to pay after having sex with her.

Suarez and the second woman, still unidentified, left the Caribe between 9:30 and 10 a.m. They were escorted to a nearby taxi stand by police officers who’d responded to the ruckus in the hotel hallway.

Once they got into the taxi, Suarez and her girlfriend talked about their misadventure.

Suarez’s friend was puzzled that her date had declined to have sex with her.

“Aren’t I pretty?” she asked the cab driver, Jose Pena, as he drove away from the Caribe on Cartagena’s busy seaside highway.

Suarez recalled that her date was a cheapskate. He’d promised to pay $250 for sex but had given her only about $30. After she complained in the hallway, men in other rooms pitched in and gave her $100.

In her first interview in The New York Times last week, Suarez was quoted as saying that the promised amount was $800. She hasn’t denied that statement, but Pena said she didn’t mention that figure in his presence.

While fallout from the scandal has engulfed Pena, Suarez and U.S. security personnel, little has emerged about how all the agents and military men in question came to meet the women. Encounters with more than 20 women have been rumored, but not confirmed.