MEXICO CITY - Ninety Cubans have broken out of the Siglo XXI migrant detention centre in southern Mexico, the latest escape of migrants at the overextended facility.

The National Migration Institute says the migrants escaped in the very early hours of Sunday, causing minor damage to the facility in Tapachula, a town in Chiapas state.

It was the second such breakout at the centre in recent weeks, as Mexican officials slowly sort through arrivals at Mexico’s southern border and hand out a dwindling number of humanitarian visas to migrants trying to reach the U.S. More than 600 Cubans fled the centre in late April, and Mexico flew 170 Cubans home last week.

Frustrated by long waits for visas and overcrowding at shelters, many migrants are opting to continue north without Mexico’s blessing.