Haitian police said Jovenel Moïse had been killed earlier this week by an armed group of 28 foreign mercenaries.
Agents also said the group included mostly retired Colombians soldiers and two Haitian-Americans.
Seventeen were arrested after a shooting in Port-au-Prince, the Haitian capital.
Some were detained in the house where they stayed, and others were found upon entering Taiwan’s diplomatic compound.
Taiwan later confirmed that authorities had arrested 11 of the men after breaking into a courtyard of the compound.
According to official reports, the police killed three suspects and were still trying to find eight.
On Thursday, the media showed the suspects arrested, bruised and bloodied, along with a large number of seized firearms and axes.
The suspects also had sets of US dollar bills, the server containing the surveillance camera footage from the president’s residence and his wallet, Le Nouvelliste newspaper said.
However, it is unclear who organized the attack or the motive behind the shooting.
The gunmen stormed the president’s home in Port-au-Prince early Wednesday morning, shooting him dead and wounding his wife, Martine Moïse.
Mr. Moïse was found with 12 gunshot wounds and a gouged eye. His wife was flown to Florida for treatment after being seriously injured.
After the attack, angry civilians joined the search for the suspects and helped police locate some suspects hiding in the bushes, authorities said.
Additionally, a crowd set three of their cars on fire but destroyed important evidence.
In response, Police Chief Leon Charles called for calm, saying that people should not take the law into their own hands.
He said the foreigners had gone to Haiti to kill the president and showed the passports of the suspects, who sat on the floor behind him in handcuffs.
Colombian Police Director General Jorge Luis Vargas said 17 former Colombian soldiers were believed to have been involved in the attack.
Also, the Colombian government committed to helping the Haitian authorities with the investigation processes.
Meanwhile, US and Canadian media identified one of the arrested dual citizens as James Solages, a 35-year-old man from Florida.
Mr. Solages, a former bodyguard at the Canadian embassy in Haiti, had allegedly said that he and the other US citizen, Joseph Vincent, were the mercenaries’ translators.
He stated that they had found the job on the Internet, adding: “The mission was to arrest President Jovenel Moïse… and not to kill him.”
On Friday, the United States said it would send officials from the Department of Homeland Security and the FBI to Haiti following the government’s request to assist in the investigation.
Besides, members of Mr. Moïse’s security team were summoned to court to explain their failings.