Officials in Dallas said the city's emergency siren system was hacked Friday night, setting all 156 sirens blaring multiple times in the middle of the night.
But now Dallas officials say the late-night alarms were due to a security breach. Earlier, the city reported the system had malfunctioned.
Dallas' 156 sirens, normally used to warn of tornadoes and other unsafe weather, were triggered at 11:42 p.m. CDT on Friday.
Technicians were trying to determine how to bring the system back online without the risk of it being hacked again, he said.
Vaz says investigators have asked the Federal Communications Commission to help determine who was behind the hack.
The city can not say how the system was hacked, but it believes the hack was done within the Dallas area.
The sirens sounded off from around 11:42 p.m. Friday night and were shut down at 1:17 a.m. Saturday morning, completing around 15 cycles of a 90-second emergency warning.
Tornado sirens sounding in Dallas. They won't know the health of the sirens until the system is reactivated. "Right now, our priority is to work on reactivating our system".
Dallas Mayor Mike Rawlings promised the perpetrator would be found and prosecuted.
About 1 a.m. Garland police said that city's sirens were going off in error as well and that they were working to fix them. "It's a costly proposition, which is why every dollar of taxpayer money must be spent with critical needs such as this in mind".