There's a lot of copper lying around the U.S., in cellular towers, telephone lines, electrical sub-stations and even vacant homes, and ripping it up and stealing it has become a lucrative activity for organized gangs and drug addicts over the past few years, according to the FBI.

Such thefts are typically prosecuted by local authorities but the FBI is now taking it more seriously, the agency said in a . "On the surface, it could be a relatively small theft," the FBI said, quoting an unnamed field agent. "But the public safety impact could be significant."

"While copper thieves may not intend to compromise critical infrastructure, they can still be charged with more weighty federal crimes," the FBI said.

In the past year, copper thefts have wrought havoc with Federal Aviation Administration towers in Ohio and with a tornado warning system in Jackson, Mississippi. And in May, about 4,000 residents of Polk County, Florida, lost power after thieves stole copper from a local transformer, the FBI said.

They also kept the "Yappin with Yohe" radio talk show off the air in Ashland, Kentucky, according to a . During the early morning hours of Aug. 21, the thieves climbed poles and cut down 600 feet of copper phone cable, knocking local radio station WLCG offline and disrupting phone service to 900 customers.