Residents across Fort Worth were jarred from their sleep early Thursday after all 153 emergency warning sirens run by the city apparently sounded inadvertently."We're very concerned the system malfunctioned the way it did and inconvenienced everyone, and we're sorry for that," said Juan Ortiz, the city's emergency management coordinator.Ortiz blamed an unprecedented systemwide malfunction and said the sirens sounded for 30 seconds to two minutes about 1:30 a.m. Officials said that the problem was reported at 1:34 a.m. and that emergency management officials secured the system by 2:03 a.m.Richard Harrison, Fort Worth fire battalion chief, wrote in a 2:30 a.m. email to reporters "Sirens inadvertently activated about 1:30 a.m. in various locations. All sirens are off at this time and cause is being investigated."Some confused, sleepy and jittery residents took to social media or their telephones immediately after the sirens sounded to find out what was going on."Just as I was about to go to bed, the sirens start going off in my neighborhood. What's going on Fort Worth?" one resident asked on Twitter."Taking a lot of calls from confused, half-awake callers," tweeted Kristen Orsborn, a morning show producer at WFAA.The National Weather Service tweeted a calming message shortly after the sirens sounded: "Be Advised. There is NO hazardous weather/events in the area!"It was unclear early Thursday how many sirens sounded.Fort Worth's outdoor warning system consists of 149 sirens located around the city. A few others are in surrounding cities, such as Haslet and White Settlement, totaling 153.They are activated during extreme weather threats such as tornado warnings and sustained winds in excess of 60 mph, but also during chemical spills or state and national emergencies.When the sirens are activated, residents are supposed to "seek sturdy shelter immediately. Make your way to an interior room, away from windows and exterior walls, and turn on a radio or television to a local station for more information," according to the city's website.