Hackers are being blamed for giving Dallas residents a rude awakening Friday night when they set off 156 emergency sirens.

The breach began late Friday local time in part of the system that communicates with all the city's sirens, Rocky Vaz, head of the city's Office of Emergency Management, said at a news conference Saturday. The siren system was deactivated at around 1:20 a.m. Saturday while investigators tried to determine what triggered the alarms, CBS Dallas/Fort Worth reports.

"We shut it down as quickly as we could, taking into consideration all of the precautions and protocols we had to take to make sure that we were not compromising our 156 siren system," he said.

The city didn't say how the system was hacked, but it suspects the hack originated from within the Dallas area. The city said it is working to install safeguards to prevent these types of hacks from occurring in the future.