The unusually large numbers are what caused agents in the Border Patrol’s Rio Grande Valley sector this week to release some migrant families at an early stage, the agency said. The releases bypassed the usual procedure in which newly arrived migrants are handed over after initial processing to another federal agency, Immigration and Customs Enforcement, which may detain them or release them with some requirement that they will show up for future court appearances.

Instead, migrants traveling in families are being released directly by Customs and Border Protection, the Border Patrol’s parent agency, after being given papers instructing them to show up at a later date in immigration court. Local officials were told that Border Patrol facilities in the area were over capacity by about 2,100 migrants.

The Border Patrol said in a statement that the recent increase in apprehensions led to a “limited availability of space” at the agency’s facilities in the Rio Grande Valley sector. Out of concern for the safety of officers and migrants, the agency said it had begun to release families after giving them a notice to appear in immigration court.

“R.G.V. Sector will continue to coordinate with state and local stakeholders and nongovernmental organizations while these temporary measures are in place,” the agency said.

The recent releases resembled a similar series of unannounced mass releases of migrants late last year in El Paso and San Diego. This time, however, federal immigration agencies appeared to be coordinating more closely with local officials, who in December had been caught off guard.

The mass release in McAllen has caused a ripple effect along the Texas border. Officials in Brownsville, 60 miles east of McAllen, were told by Border Patrol officials to expect releases there in the coming days as well. It appeared that the Border Patrol intended to ease pressure on the McAllen shelter network by putting migrants on buses and dropping them off in Brownsville.