Dallas officials don’t know who caused the city’s emergency sirens to sound off for an hour and a half Friday night, but in an update Monday, they said it wasn’t a computer hack.
City Manager T.C. Broadnax on Monday morning said the emergency alarm system is controlled by radio signals and activated by encrypted transmitters, so the issue isn't computer-based, The Dallas Morning News reports. Broadnax said as officials were restoring the system over the weekend, they added more encryption to “prevent this type of error from occurring going forward.”
The city had to manually shut down parts of the system to turn off the city's 156 alarms — usually heard only during weather emergencies.
"It does appear at this time that it was a hack," said Sana Syed, the city's public information officer, during a news conference Saturday, "and we do believe that this came from the Dallas area."
City officials are working with the Federal Communications Commission to figure out the details behind the hack, said Rocky Vaz, the city's emergency management director said Saturday.
The Dallas Police Department is leading the investigation, and it's working with the FBI and other agencies, Broadnax told City Council members Monday morning.
Broadnax told council members he's also ordered a review of other systems to see if anything else is vulnerable -- from the city's water system to 911 to police and fire dispatch. Broadnax said he wants to make sure "we are prepared for any types of outward malicious attacks."
The incident, initially labeled a "system malfunction," sparked an avalanche of worried posts on social media and calls to the emergency 911 system overnight Friday.
Syed said that they had about 4,400 calls from about 11:30 p.m. Friday to about 3 a.m. Saturday. She said that usually from 11 p.m. to 7 a.m. they get about half that number of calls.
The largest surge came from 12 a.m. to 12:15 a.m., when about 800 calls were received. The longest wait time was six minutes.
The Associated Press contributed to this report.