The state attorney general for New York has sent the five largest U.S. cellphone carriers each a letter asking why they all oppose the installation of a "kill-switch" device in their handsets as a deterrent against smartphone theft.
In the letter, Eric Schneiderman alludes to possible collusion between the carriers on the decision.
The letter follows media reports last month that the big five carriers have refused proposals by smartphone maker Samsung to install a software locking system that would render a phone useless if it is stolen.
Smartphone theft accounts for around half of all street crime in New York City and is similarly a large problem in other major U.S. cities. In recent months Schneiderman and San Francisco District Attorney George Gascón have been putting pressure on the industry to do something about the problem.
In his letters, Schneiderman told each company that he noted the five big carriers "reached exactly the same competitive decision at about the same time" and said this parallel rejection was "problematic" and "raised real questions about the independence of [the] decision."
"I note the close business ties that AT&T and the other major carriers enjoy with the CTIA -- the trade association which reportedly coordinates the industry's response to kill-switch technology -- and with Asurion -- the company that provides theft and loss insurance to consumers through every U.S. carrier," he said in a letter to AT&T. Letters to Sprint, T-Mobile, U.S. Cellular and Verizon Wireless were similarly worded.
Schneiderman asked each carrier for an explanation of its decision to reject the Samsung kill-switch and to report on if they communicated with or made any agreement with Asurion, the CTIA or a competing carrier. If so, he also asked for details of the communications or agreement and their rationale for rejecting Samsung's technology while accepting a similar software update proposed by Apple.
The message from Schneiderman was clear: The carriers could be facing possible legal action for the decision.
To underline that, he closed his letter by asking them to retain all documents related to the issues and to contact the New York State Antitrust Bureau with any questions.
The carriers have until Dec. 31 to respond.
The Samsung proposal came after Schneiderman and Gascón sent a joint letter to the smartphone maker in May this year asking why it wasn't doing more to deter theft when advertising its commitment to security and safety. Apple, Google and Microsoft received similar letters.
Apple added new security features to its iPhone and iPad devices -- the most-stolen portable electronics items -- with the introduction of iOS 7.
Martyn Williams covers mobile telecoms, Silicon Valley and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is martyn_williams@idg.com