BAGHDAD, Iraq (CNN) -- Allegations that five U.S. contractors detained inside Baghdad's Green Zone were somehow involved in the death of another American contractor last month are "completely false," a son of one of the detainees told CNN Sunday.
In a CNN exclusive, video shows U.S. contractors taken into custody by Iraqi authorities.
Four of the five detained contractors work for North Carolina-based Corporate Training Unlimited -- a security firm headed by Donald Feeney, who, along with his son, Donald Feeney III, has been detained, according to another son, John Feeney. A fifth contractor works in Baghdad for another company.
"We're pretty sure they will be questioned there in the next couple of days and released with no charges," John Feeney said, adding the men appeared in court Sunday and were scheduled for another hearing Monday.
CTU was founded by the elder Feeney, a former member of the elite anti-terrorist unit, the Delta Force, sources with knowledge of the case told CNN Sunday. The company in Fayetteville, North Carolina, has been operating in Iraq since 2003, according to its Web site.
Iraqi and U.S. personnel took the five into custody early Friday in connection with the killing of contractor James Kitterman, according to an Iraqi official involved in the investigation and another source with knowledge of the case.
Three of them allegedly had direct involvement in the death, according to an Iraqi security source. None of the men have been charged.
Kitterman was found bound, blindfolded and fatally stabbed in a car in the district, formally known as the International Zone, on May 22. The 60-year-old Houston, Texas, resident owned a construction company that operated in Iraq.
The U.S. Embassy in Baghdad confirmed that Iraqi authorities took five U.S. citizens into custody. The embassy said the men were not detained on suspicion of murder, but for an unrelated matter.
The five were being held by Iraqi security forces Sunday at a jail inside the heavily protected Green Zone, the Iraqi official said. They have been in custody for three days.
"They have lawyers there on the ground with them," John Feeney told CNN. "They have been there with them the whole time. We have people there who work for us who are bringing them food, clothes -- whatever they need. They're being treated well, and the State Department and the FBI are also involved."
The troops also confiscated weapons during the pre-dawn raid on the suspects' firm, said the Iraqi official, who spoke on condition of anonymity.
The four CTU detainees were identified by multiple sources as: Donald Feeney and Donald Feeney III; Micah Milligan; and Mark Bridges. John Feeney identified the fifth detainee as Jason Jones, who works for another company.
A source close to the suspects, who asked not to be identified, said each of the five men insisted they have alibis that would clear them and that they are anxious to tell their stories to a judge.
John Feeney said his father was "not even in the country" at the time of Kitterman's killing. He was heading back from the Philippines to make arrangements after the death of another CTU employee at the time.
The U.S. Embassy would not confirm the names of the detainees, citing privacy laws. But a spokesman said consular officials have visited with them and "they appeared well." Embassy officials have been visiting them frequently, the Iraqi security source said.
The U.S. State Department and the Iraqi government will negotiate to determine what happens next, according to the Iraqi security source close to the investigation who requested anonymity because of the sensitivity of the case. Iraqi jail workers are treating the five contractors very well and with respect, he said.
The Feeneys had known Kitterman for six years from their time in the Green Zone and "respected him," CTU spokeswoman Sarah Smith told CNN.
"Just being in the Green Zone for six years, they became very close," she said, adding, "Everyone is deeply upset about the loss of Jim Kitterman and our deepest sympathy goes to his family."
If the suspects are charged and referred to trial, the case would be sent to Iraq's Central Criminal Court, the Iraqi official said.
If that happens, it would mark the first time U.S. citizens go to trial in that country since the United States returned the nation's government to the Iraqis.
CNN's Mohammed Tawfeeq, Phil Black, Jomana Karadsheh, Alan Duke and and Samira Simone contributed to this report.