The U.S. government is temporarily barring passengers on certain flights originating in eight other countries from bringing laptops, iPads, cameras and most other electronics in carry-on luggage starting Tuesday. The reason for the ban was not immediately clear. U.S. security officials would not comment. The ban was revealed on Monday in statements from Royal Jordanian Airlines and the official news agency of Saudi Arabia.

The reason for the ban was not immediately clear. U.S. security officials would not comment. The ban was revealed on Monday in statements from Royal Jordanian Airlines and the official news agency of Saudi Arabia. A second U.S. official said the ban will affect nine airlines in total, and the Transportation Security Administration will inform the affected airlines at 3 a.m. Eastern time Tuesday.

The ban would begin just before Wednesday’s meeting of the U.S.-led coalition against the Islamic State group in Washington. A number of top Arab officials were expected to attend the State Department gathering. It was unclear whether their travel plans were related to any increased worry about security threats. Most major airports in the United States have a computer tomography or CT scanner for checked baggage, which creates a detailed picture of a bag’s contents. They can warn an operator of potentially dangerous material, and may provide better security than the X-ray machines used to screen passengers and their carry-on bags. All checked baggage must be screened for explosives.