Travelers flying to the United States from Europe and the Middle East should make sure their electronic devices are charged before boarding their flights, a new Transportation Security Administration policy dictates.

The TSA announced Sunday that passengers may be asked to turn on their devices, including cell phones, for examination during security screenings for international direct flights bound for the U.S. 

Devices that don’t have power will not be allowed on planes, the TSA said in a statement. Passengers carrying such devices may face additional screening, as well.

While the agency did not specify which airports are targeted, an official told the BBC that London’s Heathrow was among them. 

The changes come as part of the enhanced security measures put in place by the Department of Homeland Security last week, which are reportedly a response to new threats related to terror groups creating explosives that are difficult to detect. Officials believe members of Yemen-based al-Qaeda in the Arabian Peninsula have developed technologies to transform phones into explosive devices.