Dallas officials believe the city's emergency alarm system was hacked Friday night, causing sirens across the city to sound off in error shortly before midnight.
An earlier version of this story was corrected to show that the system was completely shut off by 1:20 a.m. Saturday, not 1:20 p.m.
The FCC was notified to assist in identifying the source of hack, according to city officials.
According to Dallas PIO director Sana Syed, there was no emergency or weather alert.
City officials hope to have the system up and running by Sunday or Monday at the latest. "We are putting in safeguards to ensure this type of hack does not happen again".
Dallas City Fire and Rescue had to visit each individual siren site to manually turn them off. A Google Trends feature revealed that the peak time people were searching online for information on why the sirens were blaring was at 11:48 p.m.
Original: That was one way to bring the city together-the 156 sirens that stretch from the border with Lancaster all the way north of 635, ringing for hours for no apparent reason, all of your friends flocking to Twitter for the quips. There are 156 outdoor warning sirens in the city of Dallas. They won't know the health of the sirens until the system is reactivated.
Residents are asked to be patient and to avoid calling 911 or 311 as the sirens may sound again during reactivation.
The hacker tricked the system to send repeat signals activating each siren 60 times during the night, Vaz said.