Shortly before midnight on Friday in Dallas, Texas, the city's emergency sirens started to howl. Within minutes, all 156 of the sirens were blaring out and residents were starting to panic.

The city's 911 emergency response system started to buckle under the strain of concerned residents calling in to report the disturbance. It took more than six minutes to get through to a human operator as more than 800 people rang in during the first 15 minutes. It usually takes 10 seconds to get through. But there was no emergency.

Initial reports suggested that the emergency response system had suffered a malfunction. However, officials then put out a statement blaming the incident on unknown hackers, who did not use the city's computer systems but instead carried out the scam using radio waves.

The siren system is designed to be activated when severe storms approach the city. When a major weather alert is received, a message is sent out via radio to all the sirens and, although Dallas city management aren't being specific, it appears hackers managed to mimic this system.

"Last night's hack was an attack on our emergency notification system. We will work to identify and prosecute those responsible," said the city's Mayor Mike Rawlings.

"This is yet another serious example of the need for us to upgrade and better safeguard our city's technology infrastructure. It's a costly proposition, which is why every dollar of taxpayer money must be spent with critical needs such as this in mind."

During the attack, which started at 11.41pm local time, city workers had to go around to each siren and turn them off manually, which took until 01.17am on Saturday. The system was reset and engineers began trying to figure out how hackers managed to disturb the start to everyone's weekend.

According to a Dallas City Council spokeswoman, the emergency alert system is up and running again. Engineers are also checking the system, radio network, 911/311, police-fire dispatch, flood warning system, financial systems and more. It has asked the FCC for help in identifying the source of the attack.

In a press conference on Monday, city manager TC Broadnax told journalists that he was now confident that the city's emergency response systems were locked down. He said that, with storm systems on the way, the response system is ready in the event of an emergency. ®