The leader of the nation's largest sheriff's department expects federal drug agents will attempt to step up marijuana enforcement as California moves forward with legalization. But he believes there isn't the manpower to conduct widespread raids on growers and businesses selling marijuana.

In a wide-ranging interview with The Associated Press on Tuesday, Los Angeles County Sheriff Jim McDonnell also decried California legislation that would make the state a sanctuary for immigrants in the country illegally by limiting how much local law enforcement agencies can work with federal immigration authorities. McDonnell said he doesn't want his deputies acting as de facto immigration agents, but he believes the bill goes too far and would hamper cooperation on counterterrorism and gang initiatives.

McDonnell said he expects legalization of recreational marijuana to bring additional challenges for his deputies, who patrol nearly 4,000 square miles in Southern California, from an increase in fatal traffic collisions to a rise in overdoses caused by brownies, gummies and other edibles that deliver uneven dosages of THC, the chemical compound that provides the high.

U.S. Attorney General Jeff Sessions said last month that federal officials would try to adopt "reasonable policies" for enforcement of federal anti-marijuana laws. Sessions has said he believes violence surrounds sales and use of the drug in the U.S. The Justice Department didn't immediately respond to a request for comment Tuesday.

McDonnell said it's likely there will be federal raids targeting the marijuana industry in California.

"To be able to set the tone, they may do that," he said.

Los Angeles sheriff's deputies have been preparing for the legalization of recreational marijuana in California, which goes into effect on Jan. 1, by studying crime rates in Colorado and Washington after marijuana was legalized there.

McDonnell said officials need to prepare for a potential "health crisis."

"We've seen an increase of the number of kids, in particular, admitted to emergency rooms for ingestion of edibles that in a young kid could be fatal," McDonnell said. "Somebody cuts a corner of a brownie, do they get the full ingestion of THC that was supposed to go into that whole plate of brownies or do they get nothing? There's no control."

McDonnell said anticipates that legalization will also drive up crime and will being heavy costs to train more officers to be able to identify drugged drivers.

"We don't have anything where it's similar to getting a blood-alcohol content level, as we would do in the field now," he said. "Without a definitive metric to be able to go to court with that — an index if you will — it's going to be difficult to go to court and get the prosecutions the way we know get for alcohol."

McDonnell, who has led the sheriff's department since 2014, also criticized proposed sanctuary state legislation, known as Senate Bill 54, that he said will have unintended consequences. Still, he said, the department must maintain a strict policy over what information it shares with U.S. Immigration and Customs Enforcement officials.

"Our currency is public trust, and if we're out there doing the job of immigration then we lose that," McDonnell said. "It prohibits communications between local and federal law enforcement on a number of fronts, particularly focused on immigration issues."

If immigration agents can't access the county jail to arrest immigrants living in the country illegally who have committed serious crimes, they will instead be forced to make arrests at their homes or in public places, McDonnell said.

"They will not only take him, but potentially his family and anyone around who is potentially undocumented," he said. "So we're going to be pushing them into a position we're all trying to avoid and again, eroding the trust of many of our communities."

McDonnell also condemned a series of criminal justice reform measures aimed at easing overcrowding in state prisons that he attributed to a rise in violent crime.