Police in at least four northeastern Dallas suburbs say they're trying to determine what prevented people from being able to make emergency 911 calls.
Service to Garland, Wylie, Plano (PLAY'-noh) and Rowlett (row-LET') had been restored by 3 p.m. Monday after problems arose earlier in the morning.
Plano officials say some T-Mobile customers were able to call 911 but were not being heard when a dispatcher answers.
Rowlett police say its 911 problem appeared to involve callers using various carriers.
Dallas has had its own problems with 911 communications, including early this year. The city has contended with staffing shortages and technological problems that have resulted at times in hundreds of callers being placed on hold.