Two men who had died at the hands of Haitian police and 15 others under suspicion "may have belonged to the national army" of Colombia, having left it between 2018 and 2020, general Jorge Luis Vargas told a press conference.

Moise was shot dead in a pre-dawn attack Wednesday by a 28-member hit squad made up of 26 Colombians and two Americans of Haitian origin, according to Port-au-Prince. The president's wife, Martine, was wounded.

The Colombian authorities provided no further information on the men's army careers or the reason for their departure from service.

Two of the suspects flew from Bogota to Panama on May 6 and from there to Santo Domingo, capital of the Dominican Republic, where they stayed four days before taking a flight to Haiti, according to Vargas.

The other Colombians arrived in the Dominican Republic -- which shares the island of Hispaniola with Haiti -- on June 4, and travelled to Port-au-Prince two days later.

Colombia has said it has information on four companies' involvement in the crime, without giving further detail.

President Ivan Duque earlier announced that Colombia will send an intelligence mission to Haiti to aid in the investigation.

Haiti's police chief Leon Charles has said three members of the hit squad were killed by police and 17 taken into custody. Eight remain at large.

Colombia's El Tiempo newspaper said among those arrested was Manuel Antonio Grosso Guarin, 40, one of the country's most experienced soldiers.

Another was Francisco Eladio Uribe, who, according to his partner, left the army in 2019 after a 20-year career.

The partner, identified only as Yuli, told a radio station Uribe was recruited by a security company that offered body guard services.