The Dominican Republic has sent hundreds of soldiers to its border with Haiti to make it harder for migrants without legal residency to enter the country after returning home to spend the holidays, the Associated Press reports.

A contingent of 900 troops was dispatched as part of what officials are calling Operation Shield. They were joining about 1,200 soldiers already assigned to patrol the area that divides the island of Hispaniola.

The deployment announced Tuesday is part of a broader crackdown on illegal immigration. Last year, the government issued residency permits to 184,000 people who could prove they had been living in the country since before October 2011.

An estimated 300,000 are thought to be in the country without legal status. Officials have warned that anyone without legal residency may face deportation.