WEST MIFFLIN, Pa.—Verizon has restored landline 911 service to residents of some suburbs east and southeast of Pittsburgh.

Verizon officials say some residents in West Mifflin, McKeesport and Duquesne were getting busy signals when calling the emergency number from their home telephones. Those people were urged to use their cell phones in case of an emergency.

The outage began about 1:15 a.m. Thursday and was fixed about 8 a.m. It had also affected areas in and near the Allegheny County Airport.

A Verizon spokesman says a problem at a network facility in West Mifflin caused the problem. Technicians aren't sure what caused the problem, but don't believe it was related to severe thunderstorms which brought high winds and golf ball-sized hail to those same areas on Wednesday.