WASHINGTON, July 14 (Reuters) - U.S. investigators are studying the backgrounds of Colombian mercenaries accused of assassinating Haiti"s president last week to see if any of them had past ties to U.S. government agencies, a U.S. source familiar with the investigation said. Seventeen Colombians and two Haitian-Americans were arrested last week by Haitian authorities and accused of shooting President Jovenel Moise dead in his home, an event that further destabilized the poor Caribbean nation. The source said that so far U.S. investigators have not found hard evidence of any connections between the Colombian suspects, who include former members of the Colombian military, and the U.S. government. But they believe some evidence of links are likely to turn up. One of the two Haitian-American men arrested and accused of taking part in the assassination was a former informant for the U.S. Drug Enforcement Administration, the DEA said on Monday. Two U.S. government sources identified him as Joseph Vincent, 55, of Florida. Vincent and the other Haitian-American man accused of joining the assassination, James Solages, 35, told a source they acted as interpreters. Meanwhile, court documents and a defense lawyer said that a Haitian living in Florida who Haitian investigators want to talk to about Moise"s murder cooperated with the DEA in a large-scale drug trafficking investigation. Rodolphe Jaar, who was jailed by U.S. federal authorities in 2015 for his alleged role in a conspiracy to smuggle cocaine via Haiti, is the subject of a wanted poster which Haitian police issued related to the assassination. Documents filed in Federal court in Miami, Florida, allege that Jaar "conspired to have a portion of a 420 kilogram cocaine load that arrived in Haiti," from Colombia or Venezuela in February 2012 and was ultimately headed for the United States set aside "for his personal gain/interest." At a sentencing hearing in 2014, a federal prosecutor told the court that Jaar "was cooperating with the DEA at the time of the offense, making them aware of a drug shipment that was coming into Haiti", and that "because of his efforts" the DEA was able to seize more than half of the drugs and make an arrest. Prosecutors recommended a reduced prison sentence for Jaar due to his cooperation. A third Haitian-American, Christian Emmanuel Sanon, was arrested on Sunday by Haitian authorities, who accused him of being a mastermind of the attack.