MONTPELIER, Vt. (AP) – Officials running Vermont’s Enhanced 911 emergency calling system said they were trying to determine what emergencies the system missed Wednesday when, for a period of nearly two hours, 911 calls placed in northern Vermont failed to connect.

A news release issued by David Serra, executive director of the Vermont E-911 Board, and the board’s chairman, Lamoille County Sheriff Roger Marcoux, said that at about 9:30 a.m., they began getting information that “911 calls from the northern half of the state were not being properly connected.”

The Department of Public Service, which regulates telephone companies in the state, later said the outage extended from 9:12 a.m., to 11:01 a.m., when the system became “nominally operational,” and that it became completely operational shortly after noon.

In an interview, Serra blamed the situation on the underlying telephone system run by FairPoint Communications.

“The Vermont E911 system itself is operating as it should, and callers in the southern part of the state can call into the system as usual, but we await resolution by FairPoint of the problem affecting the northern half of Vermont,” said the news release distributed at 11:25 a.m.

North Carolina-based FairPoint took over the telephone system backbone for Vermont, New Hampshire and Maine when it acquired the landline and Internet service systems in the three states from Verizon Communications in March.

A FairPoint spokeswoman, Beth Fastiggi, said Wednesday, “We’re working with Microdata Systems” – the contractor that operates the state E-911 system – “and the E-911 board to determine the root cause” of the outage.

Stephen Wark, director of consumer affairs and public information at the Department of Public Service, said in an e-mail, “This type of failure is completely unacceptable and unprecedented. The state will be conducting a complete investigation to identify the cause of the failure, and to ensure that such a failure never happens again.”

Serra said he had no information about what emergencies may not have received the proper response because of calls that failed to connect, but that he was hoping to gather such information from public safety agencies.

“I don’t have any knowledge of that, but I’m sure that was the case,” he said of missed emergency calls. “We handle more than 200,000 calls a year, so it’s inconceivable to me that we wouldn’t have had some” missed calls.

Serra said 911 calls are routed from their points of origin to FairPoint aggregation points in Burlington for northern Vermont and Rutland for southern Vermont. Normally, if there’s a problem with one of those two locations, calls are routed to the other. From there they go into the E-911 system and are routed to a public safety answering point, where call answerers are trained to coach people through emergencies ranging from childbirth to CPR, and have computer mapping systems that can help speed emergency responders to the right location.

On Wednesday morning, though, calls being routed on the FairPoint system to Burlington were neither being handed off there to the E-911 system, nor rerouted to Rutland.

“The Burlington aggregation point was like a black hole this morning,” Serra said. “It was neither sending the call on to our system … nor was it, that failing, sending it to Rutland. It was doing nothing.”

Fastiggi said of Serra’s comments, “What they said about the calls not being routed to the right place is accurate. We’re still investigating why that happened.”

Wark blamed human error. “Initial investigation points to human failure in the system,” he said.

Serra said he believes the way to prevent such problems in the future would be for FairPoint to set up its system to route 911 calls to the Burlington and Rutland call aggregation centers simultaneously.

Serra said he was “satisfied with FairPoint’s response, but I’m not satisfied with the way their (call) aggregation protocol is set up.”

He added, “We (Vermont E-911) have a state-of-the-art system, but our system is only ever going to be as good as the infrastructure that supports it. There are aspects of that infrastructure that we have no control whatsoever, that belong to the telephone companies. That being the case, that would be our weakest link, I would say.”

Fastiggi said she could not comment on any system changes that might be contemplated.