Officials say system hack is why emergency sirens went off in Dallas

City officials said a hack is the reason residents in Dallas woke up to the sound of emergency sirens blaring overnight.

The hack caused all 156 city of Dallas emergency sirens to go off from 11:42 p.m. Friday until 1:17 a.m. Saturday. Crews worked that entire time to manually shut off the system, said Rocky Vaz, director of emergency management in Dallas.

There were 15 rounds of 90-second sirens that went off and despite reports overnight, no other cities had their systems go off. The incident was originally said to have been a malfunction in the system but further investigation revealed the hack, Vaz said.

Vaz said police are not involved with the investigation at this time but that the Office of Emergency Management is working closely with the FCC and has determined where the hack came into the system but not who did it. Due to security concerns, they are not releasing any details on the hack at this time.

A former emergency management official in Dallas called Vaz and said there had been a hack of the sirens in the 1990s but that it was only one or two sirens but never the entire system.

“This is a very, very rare event,” Vaz said.

Officials will continue to update the system but expect it complete by Sunday. The sirens may go off again during a reboot and residents are asked not to call 911 if they hear them, said Sana Syed, city spokeswoman.

From 11:30 p.m. until 3 a.m., the 911 call center in Dallas received about 4,400 calls, more than double the average amount and received 800 calls in one 15-minute time period, Syed said. The surge of calls caused the center to have a backup; the longest wait was six minutes. The city’s target is to answer 90 percent of calls within 10 seconds.

“We understand that people were concerned, we had people that were asking if we were being attacked because of what’s going on overseas,” Syed said. “But now that we know what happened and we’re trying to get our system back up...bare with us as we try to get everything back on track.”

Residents took to social media using #DallasSirens to express frustration, confusion and a little humor.

Azia Branson: 817-390-7547, @aziabranson