Editor’s note: This article has been updated with comment from the Grayson County Sheriff’s Office.

The Grayson County Sheriff’s Office said landline phone service in Van Alstyne, Howe, Gunter and Dorchester is expected to be fully restored by noon Friday after an outage which started Thursday morning left thousands of residents unable to place calls, including those to 911.

The agency reported the outage in a social media post at approximately 10:30 a.m. Thursday. GCSO Capt. Sarah Bigham said she did not immediately know what caused the outage, but that the interruption may have affected as many as 8,200 residents among the four cities.

“We certainly encourage those impacted by the outage to keep their cellphones handy and charged until service can be restored,” Bigham said.