US investigators believe that the same person or persons who built the crude Christmas Day 'underwear bomb' were behind the PETN-based devices hidden in packages sent from Yemen, designed to bring down an airplane.
"The thinking is it's the same person or group of people that built the underwear bomb because of the way it's put together," CNN quoted a US government official as saying.
The unnamed official, who had been briefed by multiple US authorities and law enforcement sources, said the explosive device found this time was about four times as powerful.
One package was found in Dubai in the United Arab Emirates. The other was discovered at an airport in England. On Friday, US officials said they had not taken a position on whether planes or two Chicago, Illinois, synagogues were the ultimate targets. The packages had the synagogue addresses.
Meanwhile, a woman believed to be connected to the plot to send explosive packages bound for the United States has been arrested in the Yemeni capital of Sanaa. A female relative of the woman was also being questioned by Yemeni authorities, the government official said. The relationship between the two women was not immediately known.
Authorities are looking at a specific material found in the devices and used in the foiled "underwear bomb" attempt on Christmas Day in 2009. A source close to the investigation said the type of material found in the devices was PETN, a highly explosive organic compound belonging to the same chemical family as nitroglycerin. Six grams of PETN are enough to blow a hole in the fuselage of an aircraft.
PETN was allegedly one of the components of the bomb concealed by Umar Farouk AbdulMutallab, the Nigerian man accused of trying to set off a bomb hidden in his underwear aboard a Northwest Airlines flight as it approached Detroit, Michigan, on December 25 last year. AbdulMutallab is alleged to have been carrying 80 grams of PETN in that botched attack.
"The quantity of PETN in these (new) devices was about five times the volume used at Christmas" by AbdulMutallab, Col Richard Kemp, the former chairman of the British government's Cobra Intelligence Group, said.
The plot "does appear to be a typical al Qaeda-type operation," he said. A source closely involved in the investigation said the detonating substance was Lead Azide, a "very powerful initiator" which is easily prepared and is a standard substance in detonations.
Believing that a Yemen affiliate of al-Qaeda was involved, American and British authorities said explosive devices jammed into ink toner cartridges were powerful enough to bring down a large aircraft. British authorities said they believe East Midlands Airport in central England was simply a conduit for shipment of one device to the United States.
As they studied the devices and toiled to understand the extent of the plot, authorities pointed their fingers at al- Qaeda in the Arabian Peninsula. The group is based in Yemen, a poor Arab nation that has emerged as a major operating base for al-Qaeda and other terror groups.
Authorities, meanwhile, said the explosive devices were meticulously crafted. They were "professionally" loaded and connected using an electric circuit to a mobile phone chip tucked in a printer, Dubai police said. The devices were packed in toner cartridges and designed to be detonated by a cell phone.
The package found at East Midlands Airport contained a "manipulated" toner cartridge and had white powder on it as well as wires and a circuit board. A similar package set to be shipped on a FedEx cargo plane was discovered in Dubai, officials there said.
When the Saudis warned British law enforcement that there were explosives inside the cartridge at East Midlands, the British -- using human and canines -- could not detect the material, according to a US law enforcement official familiar with investigation.
The British authorities contacted the Saudis to verify the tip, the official said. The Saudis told them to inspect the cartridge again, and that is when the British authorities discovered the material, the official said.
In response to the threat, authorities stepped up searches on Friday of cargo planes and trucks in several US cities, said law enforcement sources with detailed knowledge of the investigation.
Also on Friday, the Transportation Security Administration stopped all packages originating from Yemen. Britain has said that all cargo into or through the United Kingdom originating in Yemen have been halted. The US Postal Service also announced a temporary suspension of acceptance of inbound international mail originating in Yemen.