PORTLAND, Maine (AP) — FairPoint Communications says an unknown problem is preventing customers from getting through to customer service call centers in northern New England.

The company said Friday technical problems are preventing business, residential and repair calls from getting through. North Carolina-based FairPoint is the dominant land telephone provider in Maine, New Hampshire and Vermont after buying Verizon Communications’ land phone and Internet network in the three states last year.

A spokesman said the company is troubleshooting the problem, but hasn’t figured out the cause and doesn’t know when service will be restored.

FairPoint has placed a recording on the toll-free numbers into the call centers informing customers of the problem and asking they call back later.