Mexico will no longer allow people on nonessential travel across its southern border with Belize and Guatemala, the latter of which saw tens of thousands of migrants cross into Mexico last month.

President Andres Manuel Lopez Obrador’s administration announced Thursday that the country will impose restrictions to block traffic at ports of entry in an effort “to prevent the spread of COVID-19.” The move could affect Central Americans’ ability to get into Mexico, which would affect the number of adults, children, and families arriving on the U.S.-Mexico border amid a worsening crisis. It is not clear how Mexican authorities will respond to migrants who attempt to come over its southern border on rafts between border crossings.