TUCSON, Arizona (AP) — U.S. officials who oversee a program that guarantees jail time for immigrants caught crossing the border illegally have refused to provide information about the program's status in Yuma, Arizona.

Arizona Sens. Jeff Flake and John McCain have asked the U.S. Department of Justice to provide details about whether federal prosecutors in Yuma have scaled back Operation Streamline, the zero-tolerance program that aims to quickly prosecute migrants who have recently crossed the border.

U.S. Attorney General Eric Holder has not responded to the senators, a Flake spokeswoman said. Public affairs officials from the Department of Homeland Security, Department of Justice and the U.S. Customs and Border Protection have also refused to answer questions or confirm any changes.

A Border Patrol union president in Yuma says that first-time offenders are not being prosecuted anymore, negating the program's aim to be a deterrent.