An unclassified advisory, sent July 20 from TSA to law enforcement agencies, raised the possibility that recent activity could be "pre-attack security probes."
CNN obtained the advisory from a government source.
The TSA downplayed the significance of the advisory in a statement released to the media following its leak.
The TSA said it was one of more than 90 bulletins sent to police in the past six months "with the intent to provide as much information as possible to our front line officers."
"There is no intelligence that indicates a specific or credible threat to the homeland," the TSA said.
The advisory details four incidents from the past 11 months in which screeners found unusual objects with items that could mimic bomb components in passengers' checked or carry-on bags.
In one case last September, a couple in Baltimore, MD, checked a plastic bag with a block of processed cheese taped to another plastic bag containing a cell phone charger. Earlier this month in San Diego, CA, a passenger checked a bag containing two ice packs covered in duct tape. The ice packs had clay in them instead of the normal blue gel.
Terrorists could be testing the system, or could be conducting repeated operations to desensitize security officials, the bulletin says...
The bulletin also details a case from June in which a passenger in Milwaukee, Wisconsin, had a carry-on bag with items resembling IED components, such as a wire coil wrapped around a possible initiator, an electrical switch, batteries, three tubes and two blocks of cheese.