Keith Upchurch, The Herald-Sun (Durham, N.C.)

DURHAM – Durham’s 9-1-1 emergency service was restored early Thursday afternoon after some callers couldn’t get through for more than three hours.

Service was disrupted starting about 9 a.m. for calls to 9-1-1 at the Durham Emergency Communications Center at Durham police headquarters. The system was tested from 11:15 a.m. to 12:15 p.m. to be sure it was stable, and was back up by 12:30 p.m.

James Soukup, center director, said he was seeking an explanation from service providers Frontier and Intrado about what caused the problem.

Soukup said the system was never down completely, as some landline calls went through. The failure primarily affected cell access to 9-1-1, he said.

He said he couldn’t be sure Thursday if any calls were missed, because the investigation was continuing. Soukup said the center is not as busy at midday as other periods, averaging about 15 calls an hour.

Calls to the center’s non-emergency line (919-560-4600) continued to go through, and the “text to 9-1-1” option for Verizon Wireless customers still worked.

Soukup said emergency communications centers in the Gaston County town of Stanley, Cabarrus County and Catawba County also experienced problems Thursday, and Intrado resolved those issues.

A spokeswoman for the Durham County Sheriff’s Office said its emergency communications center wasn’t affected.

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