DALLAS (CBSDFW.COM/AP)Officials in Dallas say they’ve completed security upgrades to the city’s outdoor sirens that will prevent the kind of “malicious activation” that caused the emergency system to blare across the city in April.

Authorities said in a statement Monday that the city’s 155 sirens now have “constant encrypted communication” and that the system ” is ready to alert City of Dallas residents and guests during any emergency.”

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They say the security enhancements were completed in late May and the next round of regularly scheduled testing is set for Wednesday. It was just days after the “malicious activation” that the Dallas City Council agreed to spend up to $100,000 for security upgrades.

Authorities said hackers were able to infiltrate the warning system used to notify people of dangerous, destructive weather and activate it late on a Friday night.

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They later clarified that the false activation was not the result of computer hacking but instead caused by someone who used radio or some other transmission to broadcast tones that activated the sirens.

The whaling from kept thousands of people awake and resulted in a rash of calls that overwhelmed the 911 system. After sounding for nearly two hours, the sirens had to be shutdown manually.

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