Updated

U.S.-bound Central Americans are fleeing urban areas and hiking into the woods and low jungle for fear of being detained by Mexican officials rounding up migrants in southern Mexico.

Until recently, the streets of Arriaga bustled with migrants who would stay at cheap flophouses and shelters and hop aboard the northbound freight trains at will. The streets of the city of about 40,000 people now look empty.

Federal official Humberto Mayans said Tuesday that immigration officials have pulled 6,000 migrants off the trains they call "The Beast" but offered no details on the roundups.

Mayans was recently appointed to head the federal government's southern border improvement plans.

Residents say masked police and Mexican immigration agents launched the roundups in Arriaga about two weeks ago.