At least 1,300 mainly Cuban migrants have fled on foot from an immigration detention center on Mexico's southern border in the largest mass escape in recent memory.
The National Immigration Institute said late Thursday that 700 of the Cubans had returned voluntarily, but 600 were still on the loose.
The institute said agents inside the compound weren't armed and there was no confrontation.
Federal police with riot shields later streamed into the compound to control the situation, as a crowd of angry Cubans whose relatives were being held at the facility gathered outside.
The Cubans claimed their relatives reported overcrowding and unsanitary conditions at the facility.
The escape was embarrassing for the government, coming on the same day Mexico's top human rights official toured the facility to oversee conditions there.