Kuder acknowledged that some phones may be sold that haven't been reported stolen, but said "we can't find a stolen phone that nobody reports to us." Still, he said, even without a serial number, ecoATM allows police to look through its transactions for types of phones sold during specific periods of time.

"We can help find a list of suspects," Kuder said. "The fact of the matter is, we generate data on a scale that nobody else generates."

Henry said he was partnering with lawmakers in Baltimore County to have the devices banned there as well. County Councilman David Marks said he plans to meet with Chief James W. Johnson on the issue. Henry said he's hoping Anne Arundel County will follow suit.

In Anne Arundel, County Council Chairman Jerry Walker said he hadn't heard of the issue before. He wasn't aware of any of his colleagues working on legislation related to the kiosks.

Baltimore City Councilwoman Rochelle "Rikki" Spector said she would take the matter to the Maryland Association of Counties to try convince other local governments to ban the kiosks. "This unfortunately has legs and spreads. I'd like to see all the counties around do the same thing," she said.

Henry said one kiosk at Mondawmin Mall was removed after Baltimore police raised concerns about thefts.

"According to police, when it was operating, there was a line out the door of people trying to sell used cellphones to this machine for cash in hand," Henry said. "While the Mondawmin Mall management was willing to voluntarily remove the machine at the request of the police, there remain several of these machines in operation at malls around the edge of our city in Baltimore and Anne Arundel counties."

A spokesman for Mondawmin Mall, Greg Harris, said the mall sought to have the ecoATM kiosk removed after a few weeks in November because it attracted large crowds that were "difficult to manage," He said he had no information about the sales being traced to thefts.

"It became a challenge to handle the crowds using the kiosk," Harris said.

Kuder, of ecoATM, said the large number of people in line isn't evidence they were seeking to sell stolen phones.

"You're looking at the people who go to Mondawmin Mall and assuming they're criminals," he said. "Ninety-nine-point-nine-five percent of the time they're honest, hardworking people looking to get value."

Baltimore Sun reporters Jessica Anderson and Pamela Wood contributed to this article.