ABC News has learned that reports of so-called "Belly Bombs" have led to an urgent alert for increased scrutiny of passengers headed to the U.S. who appear to have had recent surgery.
The idea is not new, but officials say there is a fresh interest in using this tactic. Because of that, the Transportation Security Administration says people traveling to the U.S. from overseas may go through additional screening at airports.
"These measures are designed to be unpredictable, so passengers should not expect to see the same activity at every international airport," TSA spokesman Nick Kimball said. "Measures may include interaction with passengers, in addition to the use of other screening methods such as pat-downs and the use of enhanced tools and technologies."
Medical experts say a packet of explosives the size of a grapefruit could fit inside the stomach area.
"The surgeon would open the abdominal cavity and literally implant the explosive device in amongst the internal organs, right in between the intestines, the liver and the stomach," said Dr. Mark Melrose, an emergency room physician.
Most existing scanners would not be able to detect a bomb surgically implanted in a person's body. A sensitive full-body scan might show explosives. Explosive trace-detection swabs might be able to detect surgically implanted explosives. Dogs probably would not detect them in the body.
There is no intelligence pointing to a specific plot, but when the U.S. government receives information suggesting terror tactics that could threaten commercial aviation, the TSA alerts companies domestically and abroad.
Airport security has increased markedly since the Sept. 11, 2001, terror attacks. But terrorists remain interested in attacking aviation and continue to adapt to the new security measures by trying to develop ways to circumvent them.
The Associated Press contributed to this story