The findings may raise questions about whether the ban is broad enough. CNN has learned that, through a series of tests conducted late last year, the FBI determined the laptop bombs would be far more difficult for airport screeners to detect than previous versions terrorist groups have produced. The FBI testing focused on specific models of screening machines that are approved by the Transportation Security Administration and are used in the US and around the world.

“As a matter of policy, we do not publicly discuss specific intelligence information. However, evaluated intelligence indicates that terrorist groups continue to target commercial aviation, to include smuggling explosive devices in electronics,” the Department of Homeland Security told CNN in a statement. “The U.S. government continually re-assesses existing intelligence and collects new intelligence. This allows DHS and TSA to constantly evaluate our aviation security processes and policies and make enhancements when they are deemed necessary to keep passengers safe. As always, all air travelers are subject to a robust security system that employs multiple layers of security, both seen and unseen.”