Update at 4:54 p.m. ET

People flying to the U.S. on international flights may want to keep their cellphones charged: Under a new policy, these and other devices might not be allowed on the plane if they can't power up.

The Transportation Security Administration says its new guideline is aimed at certain airports that have direct flights to the U.S. Officials at those overseas facilities should require passengers to turn on electronic devices before they're allowed to board, the TSA says.

The agency didn't specify which airports it's concerned about. But a "homeland security official said last week that the changes would primarily focus on airports in Europe and the Middle East," reports CNN.

"An official told the BBC that London's Heathrow was among the airports," the British news service says. It adds that airports in France and Germany have agreed to the procedures. London's Heathrow Airporthas also issued guidance to passengers flying to the U.S.

The new rules are reportedly a pre-emptive response to terrorist groups' attempts to make their explosives harder to detect.

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