Despite the public outcry over so-called "sanctuary cities" after a California woman was murdered by an illegal immigrant released from jail in one of the cities, their number has grown to 340, and new statistics show that they release 1,000 inmates, many with violent histories, each month.

An analysis of U.S. Immigration and Customs Enforcement records finds that many towns are embracing the sanctuary city model where illegal immigrants charged with crimes are being released over the objection of ICE which seeks to deport many.

The Center for Immigration Studies said the number of cities has grown to 340, up from 276 identified in July. They provided a website map of the cities here.

The analysis is based in new information released by ICE covering January-September 2014.

Key details noted by author Jessica M. Vaughan, director of policy studies for the Center:

Between January 1 and September 30, 2014, local sanctuaries released 9,295 alien offenders that ICE was seeking to deport. More than 600 people were released at least twice.

5,947 of the criminal aliens (62 percent) had significant prior criminal histories or other publicsafety concerns even before the arrest that led to a detainer.

58 percent of those with a prior history of concern had prior felony charges or convictions; 37 percent had serious prior misdemeanor charges, and 5 percent had multiple prior misdemeanors.

2,320 of released offenders were subsequently arrested within the time period studied for new crimes after they were released by the sanctuaries.

ICE was not able to re-apprehend most of the offenders released by the sanctuaries. As of last year, 6,460 (69 percent) were still at large.

Vaughan said she hoped the analysis kick-starts efforts to stop liberal cities from ignoring ICE and releasing often violent criminals who are also in the United States illegally.

"Our elected officials must not continue to sit back and watch these sanctuary jurisdictions release thousands and thousands of deportable criminal aliens back into our communities in defiance of ICE efforts to deport them, and then witness the harm that inevitably ensues when these removable offenders strike again," he said. "There is no more obvious immigration issue on which Congress could act now than to rein in this obstruction of a vital law enforcement mission that keeps our communities safer," added the immigration expert.

Most Americans had never heard of sanctuary cities until summer when an illegal, released from in San Francisco over ICE objections, murdered a woman on one of the city's famous piers as she walked with her parents. The alleged killer, Juan Francisco Lopez-Sanchez, had been deported five times before.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com.