The Transportation Security Administration began scrutinizing containers of powders in fliers' carry-on bags last summer as part of a broader security push, and will soon ask foreign airports that send flights directly to the U.S. to do the same.

The focus is on containers holding at least 350 milliliters of powder, which is about the size of a can of soda. Starting Wednesday, TSA and airlines are going to step up awareness efforts about the change, urging passengers to pack larger containers in checked luggage and remove smaller containers from carry-on bags for separate screening, similar to small containers of liquids.

And, starting June 30, TSA will request foreign airports with non-stop U.S. flights match the effort, much as it did last summer when it began requiring passengers to remove electronics larger than cellphones from carry-on bags for separate screening.

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The security effort isn't a ban. But the risk for a traveler returning with a large container of Moroccan spice in a carry-on bag rather than checked luggage is that a checkpoint officer could force the person to throw away a suspicious powder before boarding the plane.

"For ease of travel, TSA recommends placing larger items in checked baggage prior to arriving at the security checkpoint," said Mike Bilello, a TSA spokesman. "The international aviation community and industry's actions represent collaborative approaches that greatly enhance global aviation security."

The main security concern is from improvised explosives, but TSA is also concerned about fentanyl or pepper spray in the cabin.

TSA says powders can include items like cosmetics, baby powder and protein or energy powder mixes, among others. Gun powder remains prohibited from all checked or carry-on luggage.

"We encourage people to divest certain items – especially organic items – in order to get a clearer view of what's going on inside the bag," said Mike England, a TSA spokesman. "It's something we advise people to do. We're asking our foreign partners to do what we're already doing domestically."

The effort is another example of tightening aviation security. Airport checkpoint security was federalized under TSA after the terrorist hijackings Sept. 11, 2001, and has become stricter in recent years with developments of non-metallic explosives.

Earlier steps include:

►September 2006: restricting containers of liquids, gels and aerosols to 3.3 ounces in carry-on bags, after a trans-Atlantic bomb plot that was foiled.

►March 2010: installing full-body scanners at checkpoints that can detect unusual objects beneath a traveler's clothing. The effort to detect non-metallic explosives came after the underwear bomber tried to detonate an improvised explosive device on a flight from Amsterdam to Detroit in December 2009.

►July 2017: requiring travelers to remove all electronics larger than cellphones from carry-on bags for screening, after intelligence revealed terrorists trying to hide bombs in laptops.

More recently, travelers noticed more scrutiny of food in carry-on bags this spring at TSA checkpoints. The challenge for security officials is to get a good look at objects in sometimes cluttered carry-on bags.

Rather than ban snacks or containers of powders, TSA is asking travelers to remove them from carry-on bags for a better view in the X-ray. The alternative is to risk a hand search of the bag, which slows down the traveler and the line.

"Everyday items, including some foods, books and magazines, powders, and large electronics may result in additional screening," Bilello said.