MEXICO CITY (AP) — Mayors of Mexican cities on the U.S. border say they are concerned about a possible upsurge in deportations of migrants with criminal backgrounds after the U.S. Supreme Court ordered California to reduce its prison population.

The court told the state Monday it must reduce the inmate populations by 33,000 to ease overcrowding. Many California inmates are Mexican migrants. California officials say they will try to transfer the inmates to other facilities in the state.

Many of the 14 mayors gathered Friday said they are concerned by the court's order because U.S. authorities sometimes don't warn them when migrants who have served time are deported.

Mexican officials often lack systems to run background checks on deportees.