A coalition of Mexican mayors has asked the United States to stop deporting illegal immigrants who have been convicted of serious crimes in the U.S. to Mexican border cities, saying the deportations are contributing to Mexican border violence.

The request was made at a recent San Diego conference in which the mayors of four Mexican border cities and one U.S. mayor, San Diego Mayor Jerry Sanders, gathered to discuss cross-border issues.

Ciudad Juarez Mayor Jose Reyes blamed U.S. deportation policy for contributing to his city’s violence, saying that of the 80,000 people deported to Juarez in the past three years, 28,000 had U.S. criminal records — including 7,000 convicted rapists and 2,000 convicted murderers. Those criminal deportees, he said, have contributed to the violence in Juarez, which has reported more than 2,200 murders this year. Reyes and the other Mexican mayors said that when the U.S. deports criminals back to Mexico, it should fly them to their hometowns, not just bus them to the border.

But critics in America say the Mexican lawmakers are simply trying to pass the buck to the U.S. and its taxpayers. They say the Mexicans should take responsibility for their criminals, who are putting both Mexican and American lives in danger. U.S. Immigration and Customs Enforcement transports a majority of Mexican criminal aliens back to Mexico on buses. Since they’re often held in U.S. detention centers near the border prior to deportation, busing them to Mexican border cities is much less expensive than flying them to the interior of the country.