"It's pretty scary actually because I'm not very good at flying,

Federal officials are downplaying an alert sent to airport security officers that warned them to look out for terrorists practicing to carry explosive components onto aircraft.

The July 20 bulletin said security officials at airports in San Diego, Milwaukee, Houston and Baltimore have seized "wires, switches, pipes or tubes, cell phone components and dense clay-like substances," including block cheese.

There have been four seizures, involving both male and female passengers, since last September. The people with the items had no criminal history but officials called their explanations for having the items "questionable."

A TSA spokesperson told 11Alive's Elaine Reyes that the bulletin was routine and that there was no credible specific threat to the U.S. Still, the warning made some travelers at Hartsfield-Jackson Atlanta International Airport nervous.

"It's pretty scary actually because I'm not very good at flying, I'm a little nervous but I think it will go okay," said traveler Jenna Sherrill.

"I wasn't surprised, people are bent on terrorism and they can be very creative and it's good to know TSA is on top of things," said traveler David Reid.

The bulletin urged security and law enforcement personnel to be aware of "ordinary items that look like improvised explosive device components."