A problem with a 69,000-volt transmission line knocked out power in the Grove City-Mercer area for about 15 minutes Thursday night.

Randy Coleman, area manager for Pennsylvania Power Co., said 2,250 customers were in the dark until a backup generator could restore power.

Coleman said a problem occurred at about 8:20 p.m. with a transmission line that feeds a substation that supplies power around Grove City and toward Mercer.

It took crews about 15 minutes to isolate the problem and verify that the backup generator was working, he said.

At about 9:15 p.m., Coleman said, crews were still testing the line to determine the nature of the problem.