Reports of al Qaeda preparing so-called "belly bombs" designed to be surgically implanted in potential terrorists before they board airplanes have already led to increased scrutiny for anyone traveling to the U.S. who appears to have had recent surgery, U.S. officials said.
The Department of Homeland Security recently issued a bulletin warning of renewed interested in the tactic -- suspected to be the latest innovation from infamous alleged bomb maker Ibrahim Asiri. According to U.S. officials, a would-be attacker would slip through airport security, board a plane and detonate the bomb using a chemical-filled syringe.
"Al Qaeda has been working for over a year on the idea of implanting bombs surgically in human beings and they may now have actually done that," said Richard Clarke, former White House counter-terror advisor and ABC News consultant.
Though extreme, the possibility of hiding a significant explosive in the human body is possible, according to Dr. Mark Melrose, an emergency physician at Urgent Care Manhattan.
"With proper skill, a surgeon could indeed package a bomb or explosive device [and] it could be implanted inside the abdominal cavity," he told ABC News. Melrose said that if placed properly, a bomb the size of a grapefruit may not even cause the patient discomfort.
The Transportation Security Administration is preparing a "strong defense" against that possibility, TSA Administrator John Pistole said.
"We are treating the information seriously and sharing the information as a precautionary matter with our foreign counterparts and also, of course, with U.S. carriers," he said.
U.S. officials told ABC News Asiri, a young Saudi native, is behind the "belly bomb." Asiri is known for innovative, ruthless bomb plots including one instance in which he packed explosives into the rectal cavity of his 23-year-old brother Abdullah for a suicide missions targeting the head of Saudi intelligence, Prince bin Nayef. That bomb exploded prematurely, the officials said, and the only casualty was Asiri's brother.
Asiri is also credited with two other failed plots involving the bomb hidden in the underwear of a passenger on a Detroit-bound flight, and the bombs hidden in printers being shipped from Yemen to Chicago.
The Hunt for Asiri
Ibrahim Asiri is the son of a former Saudi soldier. The father told a Saudi newspaper his son was radicalized years ago, and fled the county for Yemen. In Yemen, Asiri trained in secret camps, working to perfect his bomb making, and managing to elude capture.
In November last year U.S. intelligence made capturing Asiri a top priority after the failed printer bomb plot. Those bombs were cleverly disguised inside Hewlett-Packard printers which were being shipped along with clothes and books. Asiri packed the toner cartridge with explosives and added the circuit board of a cell phone--something that did not stand out in state of the art cargo screening.
"We need to find him," John Brennan, President Obama's top anti-terrorism advisor, said at the time.
Before that, U.S. officials say Asiri was believed to be behind the notorious "underwear bomb" worn by then 23-year-old Umar Farouk Abdulmutallab that failed to detonate on Northwest Airlines Flight 253 on Christmas Day in 2009. That bomb contained the same type of explosives as U.S. officials said "belly bombs" would, according to a report by Britain's The Mirror.
ABC News' Martha Raddatz and Nasser Atta contributed to this report.