The immigration overhaul framework top senators released Monday relies heavily on more drones to patrol the border with Mexico as a key way to control the flow of illegal immigrants.

“Our legislation will increase the number of unmanned aerial vehicles,” the senators said in their framework, saying they also hope to boost border patrol agents and surveillance equipment.

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The proposal doesn’t say how many drones would be added to the federal fleet, but the reliance on drones could be problematic at a time when some in Congress are calling for a review of how law enforcement uses them.

And the Homeland Security Department’s inspector general has reported that U.S. Customs and Border Protection’s current drone program is chaotic and the agency can’t keep its drones flying at the rate it had promised.

The agency didn’t even budget for enough maintenance money to repair broken drones.

“CBP risks having substantially invested in a program that limits resources and its ability to achieve [its] mission goals,” the inspector general said earlier this month.

Border security is a critical part of any immigration bill. In 2007, voters’ fears that the border was not yet secure helped sink a push by President George W. Bush and top senators to pass immigration reform.

This time, senators said they’ll grant immediate legal status to illegal immigrants but won’t let them get in the citizenship line until the borders are more secure.

The Obama administration argues it’s made huge strides on border security during its four years in office.

Illegal crossings are down dramatically from their high in the middle of the last decade.

But a recent Government Accountability Office report found that the Border Patrol still captures only about 60 percent of all estimated illegal border crossers, and found that while the number of apprehensions of illegal immigrants is down, drug seizures are up — suggesting traffic is increasing.