Passengers traveling to the United States from some overseas airports could be asked to turn on their electronic devices to confirm that they’re operational. “Powerless devices will not be permitted onboard the aircraft,” the TSA said today in a news release. “The traveler may also undergo additional screening.” The government “felt it was important to crank … up” security at overseas airports, Homeland Security chief Jeh Johnson told NBC News on Sunday. “This is not something to overreact to or overspeculate about. But it’s something we felt was necessary.” The TSA has not disclosed which airports would see additional screening.

Although there are no specific threats, U.S. officials are concerned about bombs that could pass undetected through airport screening. Electronic devices are a particular concern, as experts believe they could be rewired to explode as soon as they’re turned on but look completely normal to the naked eye. Officials have reportedly been concerned “that bomb-makers from both the Yemen-based al-Qaida in the Arabian Peninsula and the Islamist Nusra Front, an al-Qaida affiliate in Syria, had been collaborating to develop the explosives and plots to detonate them,” notes the Guardian.