Migrants approaching the U.S. border... were enveloped with tear gas Sunday after a few tried to breach the fence separating the two countries.... Honduran migrant Ana Zuniga, 23, said she saw migrants open a small hole in concertina wire at a gap on the Mexican side of a levee, at which point U.S. agents fired tear gas at them.... Mexico’s Milenio TV also showed images of several migrants at the border trying to jump over the fence.... U.S. Border Patrol helicopters flew overhead, while U.S. agents held vigil on foot beyond the wire fence.... ... several hundred Central American migrants...