Key members of the hit squad allegedly behind the assassination of Haiti’s president Jovenel Moïse had been in the country for about three months.
According to authorities, the hit squad was preparing their attack, with others joining from the Dominican Republic last month.
Moïse was killed in his private residence in Pétion-Ville in the hills above the capital, Port-au-Prince.
On Friday it emerged that the alleged assassins – including two joint US-Haitian nationals resident in Florida and about two dozen Colombians – had assembled a cache of weapons, money, mobile phones and other equipment, including rental cars.
One of the two Americans arrested, James Solages, told investigators he had become involved after finding the job on the internet but maintained he thought he was working as an interpreter for the mostly foreign group.
Solages reportedly claimed he thought the group was going to arrest Moïse in the execution of a warrant from an investigating judge, rather than murder him.
Haitian authorities said the group comprised up to 28 foreign mercenaries, including retired Colombian soldiers.
Some were killed in a gun battle at a house in Port-au-Prince where they had taken refuge and others were detained.
Colombia’s defence minister, Diego Molano, said at least six members of the hit squad appeared to be Colombian ex-soldiers, and that he had ordered the army and police to help with the investigation.
The head of Colombia’s national intelligence directorate and the intelligence director for the national police will travel to Haiti with Interpol to help with investigations, Colombia’s president Iván Duque said.