Border agents have reported a dramatic drop in encounters with migrants from Cuba, Venezuela, Nicaragua and Haiti in recent weeks, as Republican lawmakers ramp up criticism of the administration’s border policies.

There has been a roughly 97 percent decline in encounters with migrants from those four nations who crossed the U.S.-Mexico border without authorization between December and January, according to Biden administration officials who briefed reporters Wednesday on the condition of anonymity.

On Dec. 11, the seven-day average of daily encounters with migrants from the four countries was 3,367. But on Tuesday, that seven-day average was down to 115, the administration officials said.

The administration officials attributed the reduction in border crossings to the expansion earlier this month of a migration initiative that each month would allow 30,000 migrants from those four countries to apply for a temporary immigration status known as parole.

“These expanded border enforcement measures are working,” Homeland Security Secretary Alejandro Mayorkas said in a news release Wednesday.

The parole program was also paired with additional immigration enforcement, in a “carrot-and-stick” style approach. Under the program, 30,000 migrants from those countries could also be expelled back to Mexico each month under a pandemic-related order, called the Title 42 policy, if they crossed the border without authorization.

The program was initially limited to Venezuelans, but was expanded to include migrants from Cuba, Haiti and Nicaragua in early January. According to the administration officials, roughly 1,700 migrants from those three additional countries have entered the U.S. in the last three weeks through the program, though many more have been approved.