About 200 Salvadoran soldiers arrived in Port-au-Prince on Thursday and Friday to assist in the search. Security sources confirmed the deployment to media.
The UN backed Gang Suppression Force said the contingent arrived to support search and security operations in the Plaine du Cul de Sac area outside the capital.
The troops are working with the Haitian National Police and other security partners. The force urged residents of Santo and surrounding communities to avoid areas where operations are underway.
The four Salvadoran aviation technicians went missing Sunday. Armed men ambushed their armored vehicle in Santo, in the Croix des Bouquets commune near Port-au-Prince.
The attackers opened fire and used explosives, setting the vehicle ablaze. The technicians escaped the burning vehicle but nobody has heard from them since.
Haitian authorities confirmed that the men were abducted. Their condition and whereabouts are unknown.
President Nayib Bukele announced a military rescue operation Wednesday. He demanded that the four men be returned alive and unharmed, and threatened a more forceful response if they were harmed.
He said the missing personnel were noncombatant aviation technicians whose primary duties involved medical evacuations.
His warning drew a response from Wilson Joseph, known as Lanmo San Jou. He leads the Haitian gang 400 Mawozo, which operates in the area and belongs to the Viv Ansanm gang coalition.
In a video circulated on social media, Joseph displayed large quantities of ammunition and challenged Bukele. He said he would not flee and was prepared to fight Salvadoran forces.
No gang has publicly claimed responsibility for the kidnapping.
