WATCH | FBI officials had been put on high alert for a possible terror attack last weekend just hours before a man stabbed nine in a Minnesota mall and a powerful bomb went off in a dumpster in New York City.
Alert issued Friday
Several intelligence sources and the FBI confirmed an alert was issued Friday.
FBI spokeswoman Kelly J. Langmesser, with the New York field office, said the alert was in response to the United Nations General Assembly meeting taking place this week in New York City, which is drawing world leaders to the area.
Langmesser gave no details about the incident or the devices discovered in New York City's Chelsea neighborhood, saying it was "an ongoing investigation and information would be made available as the investigation develops."
Sources tell Circa.com that a combination of increasing chatter online along with an impending UN meeting in New York had government officials concerned about possible attacks.
Heightened security at United Nations
The fact that the bomber or bombers remain on the loose has the United Nations now reassessing security.
UN spokesman Stephane Dujarric told the Associated Press that security inside is "being assessed on a constant basis," adding that security is the responsibility of the host nation.
One theory being looked at by law enforcement is whether Saturday's bomb was an effort to test targets -- a dry run of sorts -- for future planned attacks in the city.
Another theory is that the bomb maker or makers lacked the sophistication to carry off a wide-scale attack.
Injuries, no deaths
Dr. Sebastian Gorka, a professor in irregular warfare and strategy with the Institute of World Politics in Washington, D.C., said that the device that exploded in Chelsea was placed in a dumpster, which minimized its reach.
That could be the reason why the 29 victims were only wounded and not killed. In addition, the fact that the pressure cooker bomb found at the second location did not go off suggests it failed to explode.
'Someone will pick it up'
"If you're a guy who's never done this before, he may think he's going to make more shrapnel by placing it in a dumpster," Gorka said.
"Even a guy who's walked around New York for any length of time knows that if you leave a trash bag around, someone will pick it up as well and people are watching for this very thing."
Plenty of physical evidence
In New Jersey, there were no injuries after a device exploded during a Marine charity 5k race.
The device was composed of three pipe bombs, only one of which went off, leaving plenty of physical evidence for investigators to examine, federal officials said.
Four pipe bombs could have done "extraordinary damage to the onlookers and runners," Gorka said.
Officials are still investigating to see if there is any link between the New Jersey devices and the NYC bomb. Mayor Bill de Blasio said the Chelsea incident had no ties to international terror and would not call it terrorism. New York Gov. Andrew Cuomo called it "obviously terrorism," adding that the investigation was ongoing.
Gorka said the use of pressure cooker and pipe bombs bears the hallmarks of past attacks conducted by jihadist terrorists, like the Boston marathon bombings.
Dzhokhar Tsarnaev (pictured here) and his older brother Tamerlan used pressure cooker bombs in Boston that killed three people and wounded 264 others. They also used pipe bombs in their attempt to escape from law enforcement.
'Fit the M.O.'
Brian Fairchild, who spent two decades with the CIA and has testified before Congress on terrorism, said the "pipe bombs and pressure cookers seem to fit the M.O. [modus operandi]" of extremist groups.
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