AUGUSTA — State utility regulators are expanding an investigation of FairPoint Communications for failing to meet minimum service standards for landline customers.

The Maine Public Utilities Commission has been considering a $500,000 fine against FairPoint for failing to meet standards in 2014 and 2015. FairPoint had asked regulators not to open an investigation into standards that it failed to meet this year and has contended the metrics are unattainable and unnecessary in the fast-evolving telecom industry.

Commissioners agreed Tuesday to expand their investigation to the second quarter of 2016. A state law that went into effect last summer set service quality standards that FairPoint calls more reasonable.

Commissioner Mark Vannoy said the investigation likely will conclude next spring.

“The failures here are similar to past failures and appear to replicate an ongoing pattern regarding service quality,” Vannoy said. “The reasons for the poor performance are similar to those made by FairPoint to explain prior quarters’ poor performance.”

FairPoint Communications Inc., which is based in Charlotte, North Carolina, and provides telephone service in Maine, New Hampshire and Vermont, contends cyberattacks, bad weather and a four-month strike contributed to service problems in 2014 and 2015. In an August letter about problems this year, a FairPoint spokesman told commissioners the company failed to meet “unreasonably high” standards for clearing up troubles within 24 hours and unmet installation appointments.

The representative said the measures are “impossible to sustain” because of the large company’s number of installations and the fact it manages its personnel based on “customer appointments, not the 24-hour clock.”

FairPoint did not respond to a request for comment Tuesday.

The company has asked regulators to refrain from opening a formal investigation and imposing “a second layer” of penalties. The representative said if consumers think service quality is bad, the market will punish FairPoint.

The Maine Legislature this year passed a compromise law that lifts a requirement for FairPoint to provide landline access to 22 large communities where there’s adequate competition. The requirement still covers about 150 other communities.

FairPoint this month announced it is laying off at least 110 workers across Maine, New Hampshire and Vermont because of a downturn in its traditional telephone service.