According to a Verizon spokesman, a technician at Needham, Mass.-based Dictronics Inc. was doing a planned upgrade last week of a digital recorder used for 911 emergency calls and radio communications between troopers and headquarters. The work is part of a general contract for upgraded 911 equipment between the commonwealth of Massachusetts and Verizon.

After the work on June 13, Verizon officials were informed by the state police that up to 11 months' worth of recordings -- both calls and data -- were no longer accessible. Verizon spokesman John Bonomo said a preliminary analysis indicates that the incident may have been the result of an error by a Dictronics technician.

"A technician from one of the subcontractors was doing some upgrading work on the state police Public Service Answering Point system, a call center you go into when you dial 911," Bonomo said. "We don't know if it was a matter of the technician not following certain steps, or not following certain steps in certain order, or exactly what it was. But it seems like the preliminary analysis by the vendor is that the process may have been done in error."

At the request of the state government, Verizon plans to bring in specialists to attempt recovery of the data. That plan includes making mirror images of the currently inaccessible data; on-site efforts to recover the data; and, if necessary, shipping the data to outside experts, including those at the manufacturer's research and development facility, so that multiple attempts can be made to forensically recover the information.

"Part of what we're doing now is trying to determine what is on the hard drive of the equipment, what is not on there, and if it is there, where is it," Bonomo said. "It's possible the calls were deleted, but it's also possible that they're existing, but we just need to find the right path to access them."