WASHINGTON -- CBS News has learned that the Department of Homeland Security has sent an intelligence assessment to police agencies across the country about drones being used as weapons in an attack.

The bulletin went out Friday and warned that unmanned aircraft systems or drones could be used in the U.S. to advance terrorist and criminal activities. Law enforcement sources say, "emerging adversary use of Unmanned Aircraft Systems present detection and disruption challenges."

According to federal officials, "The rising trend in UAS incidents within the National Airspace System will continue, as UAS gain wider appeal with recreational users and commercial applications."

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The bulletin goes on to say, "while many of these encounters are not malicious in nature, they underscore potential security vulnerabilities... that could be used by adversaries to leverage UAS as part of an attack."

Currently, intelligence bulletins are released almost weekly as law enforcement responds to threats from ISIS sympathizers. But the release of a bulletin dedicated to the threat from UAS is unusual. The bulletin does not mention any specific upcoming events authorities are concerned about but points to the overall security challenges drones present.