A hit squad composed mostly of retired Colombian soldiers assassinated Haiti's President Jovenel Moïse earlier this week, police say.
The group included 26 Colombians and two Americans of Haitian origin, police chief Léon Charles told reporters.
Eight of the suspects are still on the run, while 17, including the two Americans, have been arrested.
The remaining suspects were shot dead during gun battles with the police in the capital, Port-au-Prince.
In the early hours of Wednesday, a group of gunmen broke into the president's home and shot him and his wife. Mr Moïse was found lying on his back with 12 bullet wounds and died at the scene, according to authorities.
His wife Martine was seriously injured and has been flown to Florida for treatment, where she is said to be in a stable condition.
It is not yet clear who planned the attack or what motivated it. Haiti's interim Prime Minister Claude Joseph, however, told the BBC that the 53-year-old president may have been targeted because he was fighting "oligarchs" in the country.
On Thursday, police presented some of the suspects to the media along with weapons, Colombian passports and other evidence. "Foreigners came to our country to kill the president," Mr Charles said.
"We will strengthen our investigation and search techniques to intercept the other eight mercenaries," he added.
Colombia's government has said at least six members of the alleged hit squad appeared to be retired members of its military. It has pledged to assist Haiti with its investigation efforts.
The US state department, meanwhile, said it could not confirm if any of its citizens had been detained.
Investigators are still searching for the masterminds of the killing, which has triggered some civil unrest in what is the poorest nation in the Americas.
An angry crowd gathered on Thursday to watch the police operation in the capital. Some cars were torched, and people gathered outside a police station where the suspects were being held.
A state of emergency remains in force across the country.