At least 10 American troops could be implicated in a widening sex scandal involving a U.S. Secret Service team preparing for a presidential visit to Colombia, officials said Tuesday.

Government investigators are probing embarrassing allegations that Secret Service agents and U.S. military service members sent to the Caribbean resort of Cartagena ahead of President Barack Obama's weekend visit consorted with prostitutes.

U.S. President Barack Obama said Sunday he expected a "rigorous" probe into a sex scandal involving Secret Service agents, warning he would be "angry" if the claims were proven true.

The incident, which saw 11 Secret Service and five military personnel pulled from their security duties in Colombia at the Summit of the Americas, overshadowed the talks attended by Obama and other regional leaders.

Leaders from across the Americas were wrapping a two-day gathering in Colombia Sunday with U.S. President Barack Obama under intense Latin American pressure to let Cuba attend future hemispheric summits.

They met in plenary session to decide whether this would be the last hemispheric summit since several Latin American leaders made it abundantly clear they would not attend in the future if Cuba was kept out.

President Barack Obama might be noticing a familiar pattern. Whether it's allegations of Secret Service personnel consorting with prostitutes, candid moments caught live on microphones or launching bombs over Libya, his foreign trips seem to get overshadowed by distractions.

That's been the case on the coast of Colombia, where Obama will wrap up a weekend summit with a news conference that may well force him to confront the latest troubles — misconduct claims against Secret Service and military personnel assigned to make Cartagena secure for his visit.

A diehard Colombian fan of Barack Obama has turned his home into his version of the White House and hopes to welcome the U.S. president with a gift when Obama attends a summit in nearby Cartagena this weekend.

Silvio Carrasquilla, an Afro-Colombian and a former mayor of the northern town of Turbaco, says he hopes to present the U.S. leader with a young donkey named "Demo." The donkey is the symbol of Obama's Democratic Party.

Pop superstar Shakira helped launch a $36 million education project for Colombian children Thursday as part of a series of events linked to the weekend Summit of the Americas.

The Colombian singer, who is scheduled to meet with U.S. President Barack Obama, will also sing her country's national anthem at the opening ceremony for the gathering of 33 democratically elected leaders of the Western Hemisphere Saturday in Cartagena.

Marxist FARC rebels attacked a Colombian army unit Saturday and killed 11 soldiers, the army said.

The troops were hit by an "indiscriminate" strike by rebels with the 10th front of the Revolutionary Armed Forces of Colombia (FARC) in Arauca department, in the east of Colombia, the army said.

Colombia's FARC rebels pledged Sunday to end decades of kidnapping civilians, a historic shift for Latin America's longest-fighting leftist guerrillas, who also vowed to release remaining police and military hostages.

"We wish to announce that in addition to our already announced plans to free six prisoners of war, we will free the four others who remain under our power," the group said in a statement published on its website.

Colombia's Marxist FARC guerrillas said Monday they were willing to negotiate with President Juan Manuel Santos, in a statement signed by the group's new leader, named just two months ago.

The Revolutionary Armed Forces of Colombia said there are "issues we are interested in dealing with at a hypothetical negotiating table," in a statement from FARC chief Timoleon 'Timochenko' Jimenez posted on a rebel website.

Leaders from across Latin America and the Caribbean pledged to work together to fend off the effects of the world financial crisis and safeguard the region's growing economies.

Several presidents stressed at the start of a two-day summit Friday that they hope to ride out turbulent times by boosting their local industries and increasing trade within the region.