Hundreds of migrants from around a dozen countries departed from Mexico’s southern border town of Ciudad Hidalgo on foot, aiming to reach the U.S. border.

Some are hoping to arrive before the November elections, fearing that if Donald Trump wins, he will fulfill his promise to close the border to asylum-seekers.

Migrants like Miguel Salazar from El Salvador worry that a new Trump administration might block the use of the CBP One app, which grants appointments for legal entry at U.S. border posts.

The app functions only once migrants reach Mexico City or northern Mexican states. Many migrants have been waiting in Ciudad Hidalgo for weeks for permits to travel north.

Large migrant groups have formed to reduce risks from gangs and Mexican immigration officials, but these caravans often disband in southern Mexico due to exhaustion, the Associated Press has reported.

Additionally, Mexico has recently made it more challenging for migrants to reach the U.S. border via buses and trains.

Written by B.C. Begley