(AP) — The federal government refuses to say whether prosecutors in Yuma, Arizona, have scaled back a years-old program that guarantees jail time for most immigrants caught crossing the border illegally and which law enforcement officials say is crucial to public safety. John McCain and Jeff Flake wrote a letter to Attorney General Eric Holder seeking information on the status of the zero-tolerance program that circumvents the civil immigration system and lumps together months' worth of criminal proceedings into one day for immigrants caught crossing the border illegally. Worsencroft said the program was a large factor in the steep decline in border-crossers in Yuma because it sent a message that even first-time offenders would serve jail time and because it allowed agents to focus their attention on drug smugglers and other dangerous criminals. Federal judges sentence large groups of immigrants within days of their arrival into the U.S.