PHOENIX — The impact of steep declines in the number of migrants illegally crossing the border with Mexico in recent years has rippled across Arizona and other border states, with federal and local law enforcement seeing big drops in crime related to illegal immigration.

In Arizona, federal agents have found far fewer drop houses, where smugglers stash border crossers. Police chiefs in Arizona cities say their crime rates are low and are falling, along with the numbers and costs of illegal immigrants coming through their jails.

Federal officials met with state and local police departments on Tuesday and Wednesday at the Border Security Expo in the convention hall in downtown Phoenix. They broadly agreed that the decrease in illegal crossers —down to about 340,000 migrants apprehended in 2011 from a peak of 1.1 million in 2005 — has lightened the workload for the police, but has also brought worrisome changes in the type of crimes they confront.

While they no longer see huge flows of illegal migrants heading for low-wage work in the United States, federal and local officials said they now faced smaller numbers of more determined and potentially more dangerous crossers, including migrants carrying illegal drugs.