SAN FRANCISCO, Jan. 1 (Xinhua) -- U.S. immigration authorities have voiced "deep concern" about California's sanctuary law after a local police officer was killed by an undocumented immigrant last Wednesday, the San Francisco Chronicle reported Monday.

U.S. Immigration and Customs Enforcement (ICE) said in an emailed statement to the San Francisco newspaper that the sanctuary law of California could put public security at risk if federal immigration officials have no full resources to seize undocumented immigrants in the state.

"We remain deeply concerned that California's sanctuary laws continue to undermine public safety and cause preventable crimes by restricting law enforcement cooperation and allowing public safety threats back into the community to reoffend," ICE spokesperson Liz Johnson said in the statement.

The ICE said it had no prior contact with the illegal alien suspect that killed the police officer last week.

Police officer Ronil Singh in Newman city of Stanislaus County, Northern California, was shot dead on Dec. 26 when he was pulling over Gustavo Perez Arriaga, who was suspected of Driving Under the Influence (DUI). The killing prompted a two-day manhunt for Arriaga, an undocumented Mexican immigrant.

Stanislaus County Sheriff Adam Christianson blamed Singh's death on the state's sanctuary law at a press conference last Friday after Arriaga was arrested.

He criticized the law for blocking local law enforcement from reporting Arriaga's status as an illegal immigrant to federal immigration officials, saying that Singh would have been alive if Arriaga had been reported to the ICE and deported for drunk driving offenses a long time ago.

Christianson added that 32-year-old Arriaga, a Mexican native, was found to have two prior DUI convictions and have ties to a criminal gang. The ICE said it now has placed a detainer on Arriaga and put in custody six others who were accused of attempting to help Arriaga flee back to Mexico.

California passed a statewide sanctuary policy that took effect in early 2018, which limited local authorities' cooperation with federal officials in enforcing the nationwide immigration law in the state.

As a sanctuary state, California said the policy was put in place to reduce the fear of deportations and family break-ups among people who are staying in the United States illegally, so that they would be more willing to report crimes to local police departments and use health or social services.

U.S. President Donald Trump has been critical of California's sanctuary policy, and cited Singh's death when ramping up his call for getting tough on border security in the southern United States.