PORT-AU-PRINCE, Haiti — At least four top Haitian security officials responsible for presidential protection have been placed under travel restrictions amid an investigation into the assassination last week of President Jovenel Moïse, Haitian prosecutor Bed-Ford Claude said Friday.

Those under departure bans include presidential security chief Dimitri Hérard, who was detained Thursday, along with other officials in question. Hérard has been removed from his position, at least for now; it is not clear if he faces formal charges.

No members of the Moïse’s security detail were injured in the attack on his private residence, in which he was slain and his wife injured.

In a letter addressed to Joseph Cianciulli, the country’s director of immigration and emigration, Claude issued a ban, affecting officials under investigation, on “leaving the national territory by air, sea and land” due to “serious suspicion of assassination of the President of the Republic.”

Beyond Hérard, those on the list include Léandre Pierre Osman, principal inspector and head of the presidential security unit; Amazan Paul Eddy, a team manager; and Jean Laguel Civil, general coordinator of presidential security.

At least two others present on the night of the assassination have been banned from leaving the country.

Claude told The Washington Post that the bans had been imposed because the officials “could attempt to flee the country.”

As the investigation unfolds, many key questions remain unanswered. More than 20 people have been arrested so far. Police have sought additional warrants and conducted some 27 interviews, Léon Charles, the head of Haiti’s National Police, said at a news conference Friday. Three suspected participants have been killed since last week, and five Haitian Americans are in custody, he said.

Haitian police are working international police bodies, including the FBI and Interpol, he said.

Several former Colombian soldiers — some of whom at one point received training from the United States, according to the Pentagon — are among those detained.

Christian Emmanuel Sanon, 63, a Haitian American self-described pastor with long ties to Florida, was arrested on suspicion of playing a leading role in the assassination effort.

Preparations for Moïse’s funeral, set for July 23, are underway, officials said.

Marine Moïse, the wife of the slain president, was critically injured in the attack. On Wednesday, the public saw her for the first time after the event in two photos posted on Twitter showing Moïse in a hospital bed with a cast.

“Thank you for the team of guardian angels who helped me through this terrible time,” she tweeted in English. “With your gentle touch, kindness and care, I was able to hold on.”

In Creole, she tweeted a thank-you to those who had prayed for her life.

“I have yet to believe that my husband left like that, under my eyes, without telling me a last word,” she wrote. “This pain will last forever.”