Researchers at IBM and Threatcare have found vulnerabilities in “smart city” devices, which are used for everything from traffic monitoring to radiation detection, the companies said Thursday.

That means hackers could potentially hijack the devices, either to create panic or to prevent the devices from detecting when a real emergency exists, says Daniel Crowley, research director at IBM X-Force Red, a security-testing unit.

“I think the danger there is that when you’re relying upon sensor data for safety reasons, and that sensor data can be corrupted either to hide when an emergency situation is happening or to create fake emergency situations and cause panic, there’s obvious danger there,” Crowley says.

The researchers say they found a total of 17 vulnerabilities across systems used in smart-city technology from Libelium, Echelon and Battelle. Each of the vendors has released patches to fix the bugs, which the researchers are announcing at the Black Hat security conference, in Las Vegas.

To test the systems, the researchers began by dissecting firmware they were able to obtain online, then later acquired some of the systems after spotting potential vulnerabilities, says Jennifer Savage, a security researcher at Threatcare. They also used specialized search engines such as Shodan and Censys, which crawl internet of things devices in order to find examples of where the devices are being used in the real world. That allowed researchers to notify relevant agencies about the risks involved.

Government agencies utilizing the systems include a European country using some of the devices for radiation testing and a U.S. city using them for traffic monitoring, the researchers say.

Some warnings systems have already been used by hackers, at least to cause mischief. Last year, a prankster set off emergency sirens across Dallas for more than 90 minutes, and hackers have previously hijacked TV emergency signals and tampered with digital road-warning signs.