The number of sanctuary cities, or jurisdictions in the United States that do not enforce federal immigration laws, has risen to about 340, resulting in the release of about 1,000 undocumented immigrants with criminal records per month.

Date obtained by the Center for Immigration Studies (CIS) showed that between Jan. 1 and Sept. 30, 2014, US sanctuaries released 9,295 alien offenders that the Immigration and Customs Enforcement (ICE) was seeking to deport. Of these, more than 600 people were released at least twice.

Last July, the CIS said ICE had identified 276 jurisdictions that had policies obstructing immigration enforcement that mainly ignore ICE detainers.

As of Oct. 5, about 340 US jurisdictions have adopted non-cooperation policies.

Of the more than 9,000 undocumented offenders, CIS said 5,947 had significant criminal histories even before their arrest that led to a detainer. A total of 57 percent of those with criminal history had felony charges or convictions, 37 percent with serious prior misdemeanor charges and 5 percent had multiple prior misdemeanors.

About 2,320 of the total were subsequently arrested after they were released by the sanctuaries.

One of them is Victor Aureliano Hernandez Ramirez who was arrested in July 2015 for raping and then bludgeoning 64-year-old Marilyn Pharis of Santa Maria, California who died eight days later. He was arrested for battery in 2014 and was in police custody when a detainer was issued by ICE to deport him. The sheriff did not comply with the detainer.

ICE has failed to re-arrest most of the released undocumented offenders. As of last year, 6,460 were still at large.

When ICE fails to take custody of undocumented offenders in jail, it sends out officers out to the streets to re-arrest them.

With the sanctuary policy obstructing deportation of offenders, Sen. David Vitter has introduced a bill that would withhold certain federal funds to sanctuaries and provide legal protections to sheriffs and police chiefs who want to cooperate with ICE.