Mexico's border mayors say they are worried about a possible surge in deportations of criminals to their cities after a U.S. Supreme Court ruling ordered California to reduce its prison population by 33,000.

Mayors of 14 border cities from Tijuana to Matamoros meeting in Mexico City on Friday say they already have problems because U.S. authorities often don't warn them when migrants with criminal records are deported to Mexico.

"There are indications they are going to clean out their prisons," said Manuel Baldenebro, mayor of the city of San Luis Rio Colorado, Sonora, which sits on the border with California and Arizona. "They (migrant inmates) are a burden, and if they are trying to economize in their jails, they see it as better to send them back."

Baldenebro said the notion of more criminals has caused "fear and insecurity" in cities already plagued by a stubborn wave of drug-related violence that has killed more than 35,000 people nationally since 2006.

While there are no tracking systems to determine what happens to deported criminals, at least one, Martin Estrada Luna, is accused of becoming a leader of a cell of the Zetas drug gang in the border state of Tamaulipas just 18 months after he was deported from the United States. Estrada, who had a long rap sheet of mostly theft and property crimes in Washington state, is now in custody in Mexico City, where he is accused for masterminding the killing of more than 250 people.

According to the California Department of Corrections and Rehabilitation, about 10 percent of its 162,694 inmates are from Mexico, the majority undocumented.

The supreme court ordered California on Monday to reduce its prison population to ease overcrowding. California officials say they are looking at a number of possible ways to comply with the ruling, including transferring inmates to local facilities. While there has been no mention of stepping up deportations, there are currently programs in the U.S. to actively identify migrants in the U.S. prison system and deport them upon release.

"Our plan will be submitted to the three-judge panel on June 6 on how the state plans to comply with the population reduction order," said corrections spokesman Terry Thornton. "It's still being worked on."

Spokesmen for Gov. Jerry Brown did not immediately return a telephone message.

Under a tough-on-crime immigration crackdown, half of the 393,000 people deported from the United States between October 2009 and September 2010 were convicted of crimes, from minor offenses to murder. While the U.S. doesn't specify their countries, the vast majority are from Mexico.

Mexicans with criminal records in the U.S. can't be detained in Mexico if they have not violated the law in their home country, and most Mexican cities don't have any way to run criminal background checks on deported inmates to see if they have pending charges in Mexico.

When Mexicans without documents finish their prison terms, they're bused to the border and freed.

The United States and Mexico are experimenting with new methods of alerting Mexico about deportations, and U.S. officials say they warn Mexico when former inmates are considered particularly dangerous.

It's not known whether they warned Mexican authorities about Estrada, who was never accused of murder in the U.S.

"What we have seen as mayors is ... that they send back migrants in the early morning hours, and sometimes they don't give us advance notice," said Everardo Villarreal, mayor of Reynosa across from McAllen, Texas.

"We have to have better coordination," added Hector Murguia, mayor of Ciudad Juarez across the border from El Paso, Texas. "It's not about throwing the fleas and cockroaches across the border. Together, we have to kill the fleas and cockroaches."


Associated Press Writer Don Thornton contributed to this report from Sacramento, California.