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Starting Saturday, the Transportation Security Administration will introduce a rule affecting the size of containers holding powdery substances. The measure applies to items packed in carry-on bags on flights bound for the United States from abroad.

With the new ruling, passengers must store such granular items as flour, sugar, ground coffee, spices, powdered milk (such as baby formula), protein powders and cosmetics in a receptacle no larger than 12 ounces, about the size of a soda can. No plastic bag required. Objects placed in bigger vessels may be subjected to additional screening at the checkpoint.

If security officials cannot identify the substance — in TSA parlance, “effectively detect and resolve powders through testing protocols” — the passenger can place the material in his or her checked luggage or toss it, but may not board the plane with it.

“There are a range of powders that could be used to irritate or harm aircraft passengers and aircrew if released during flight,” said Lisa Farbstein, a TSA spokeswoman. “TSA is working with international partners to align global aviation security standards.”

The agency adopted similar measures for domestic travel in April. For instance, passengers must place all personal electronic devices larger than a cellphone, such as e-readers and tablets, into a bin and remove dense food items that clutter bag interiors.

The focus on powders is part of a larger wave of security initiatives at airports around the world. Many carriers and countries have invested in new checkpoint technologies, amped up airport security, and introduced procedures that will better safeguard planes and passengers.