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.