D.C. Police Chief Cathy Lanier, who shamed the telecommunications industry into helping stop a spike in violent cellphone robberies last year, has turned her attention to the sudden arrival of automated vending machines that offer cash for used phones.

The new machines -- which look and work like ATMs -- encourage the theft of cellphones, Lanier told D.C. Council members during an oversight hearing Tuesday.

Six stolen cellphones have been recovered from kiosks run by ecoATM, and police suspect an additional 76 cellphones found in their kiosks were stolen, Lanier said.

The technology is part of the "new and emerging markets through which criminals are receiving money for stolen phones," she said. "We are working to close those avenues to the criminals."

Prince George's County authorities shut down a kiosk at Iverson Mall in Temple Hills last week after police learned that company had not obtained a secondhand-dealer license to do business.

San Diego-based ecoATM has installed about 16 kiosks within 50 miles of the District since September, including Fair Oaks Mall and the Fashion Centre at Pentagon City, company officials said. None of the machines is located in the District.

The D.C.-area machines have conducted tens of thousands of transactions, said company spokesman Ryan Kuder.

"We share the chief's concern with the rising theft of cellphones," Kuder said. "There are some bad apples out there, and we are addressing the issue directly."

Each transaction requires the user to display a driver's license and submit a thumbprint, and the machine snaps a photo of the user, Kuder said. The images are quickly transmitted so that an ecoATM employee can check the information in real time, he said. At the end of the day, transactions from each kiosk are collected and submitted to local law enforcement authorities for review.

Lanier has made the prevention of cellphone theft her pet project. D.C. has seen an 8 percent reduction in street robberies since last fall, when the nation's cellphone carriers created a database to disable stolen phones, Lanier said.

"It's working," Lanier said, "but it seems like every time we find a solution, there's another hole in the dam."