SAN ANTONIO, Texas (CNN) -- One of three American hostages rescued last week from Colombian rebels said Monday he believes his former captors will retaliate against those still being held.
"Right now, they're being punished because we got rescued," Marc Gonsalves said at San Antonio's Brooke Army Medical Center, where he and fellow ex-hostages Thomas Howes and Keith Stansell have been treated for days.
The Revolutionary Armed Forces of Colombia (FARC) had held the three U.S. government contractors since February 2003, after their plane crashed in a remote region of the South American country.
The three were among 15 people -- including Colombian politician Ingrid Betancourt and 11 Colombian national police and military men -- who were rescued Wednesday by the Colombian military. Read about the rescue operation
On Monday, the Americans spoke publicly for the first time since their rescue. Gonsalves, who called his rescuers "heroes," said he fears for the hostages who remain with FARC.
"They're going to get up early tomorrow morning, they're going to put a heavy backpack on their backs, and they're going to be forced to march with [a] chain around their neck while a guerrilla with an automatic weapon is holding the other end of [the] chain like a dog," Gonsalves said.
Gonsalves blasted the leftist rebel group, calling them "terrorists" who pretended to be fighting for the poor of Colombia so they could engage in crimes such as drug trafficking and extortion.
"They say they want equality; they say they just want to make Colombia a better place," Gonsalves said. "That's all a lie ... to justify their criminal activity."
He said the rebels deprive their captives of basic human rights, adding that hostages were often chained at their necks and held at gunpoint, and that he once saw the rebels keep a newborn in captivity even though the infant was ill. Watch Gonsalves describe hostages' treatment »
"They are not a revolutionary group. They are terrorists -- terrorists with a capital T," said Gonsalves, a Florida resident and Connecticut native.
He said FARC claims it is not a terrorist group, but he said it should prove that claim by freeing its remaining hostages. FARC is believed to hold more than 700 hostages in camps scattered throughout the jungle.
"Don't tell us that you're not terrorists. Show us that you're not terrorists," he said.
He said the majority of FARC forces were poor children or young adults tricked into thinking they were joining a just, revolutionary cause. Later, he said, some would regret their decision to join, but they knew they would be killed if they tried to leave.
"I've seen how their own guerillas commit suicide in a desperate attempt to escape the slavery that the FARC have condemned them to," Gonsalves said.
Before they spoke, the three contractors, along with their families, entered to cheers and a standing ovation. All three wore button-up shirts and dark suit jackets. They were photographed holding a small American flag.
Howes, the first contractor to speak, said, "Five and a half years ago, we fell off the edge of the Earth."
He thanked Northrop Grumman -- the contractor that employed him, Gonsalves and Stansell -- for supporting his family. Like Gonsalves, he called the Colombian rescuers "heroes."
"We're doing well, but we cannot forget those we left behind in captivity," he said, adding later, "It's a pleasure to be in the USA."
When it was his turn to speak, Stansell walked up carrying his twin 5-year-old sons. He said his family's ongoing support is "the reason I'm alive."
Stansell, of Florida, wrapped up his brief statement, in which he thanked the Colombian and U.S. governments, with a playful question for Gov. Charlie Crist.
"To Gov. Crist of the great state of Florida: Sir, I don't have a driver's license. How am I going to get home?" Stansell said.
The contractors thanked the news media for covering their story but declined to take questions.
From the day of their rescue until Monday, the Americans had been kept from the news media so they could undergo a reintegration process that included medical tests.
Monday's statements were part of a "yellow-ribbon ceremony" that was intended to mark the contractors' success in that process and prepare them to "attempt a normal life," said Maj. Gen. Keith Huber.
It was unclear when the men would be leaving the medical center. Officials at the center said the men are healthy.
"Although their time in captivity has been extremely difficult and at times traumatic, they have in general fared very well," Col. Jacki Hayes said. "They've shown themselves to be strong and adaptive."
Each contractor lost roughly 30 pounds during captivity, a result of strenuous activity and poor diet, the center said.
Northrop Grumman Electronic Systems President James Pitts said the company's crisis team is prepared to assist the men as they adjust to their lives as free men.
The contractors were conducting a joint U.S.-Colombian aerial counternarcotics mission in February 2003 when their aircraft made a forced landing because of mechanical failure. FARC members patrolling the area reached the aircraft and killed two crew members before taking the three captive.
FARC, which has been fighting the Colombian government and other paramilitary groups for decades, defends the taking of captives as a legitimate act of war.