An explosive device found hidden in a printer cartridge on a cargo plane at a UK airport was apparently designed to blow the aircraft out of the sky, British Prime Minister David Cameron said tonight.
Mr Cameron was speaking as Yemeni officials arrested a woman on suspicion of sending the two mail bombs, found yesterday in cargo hubs at East Midlands Airport and in Dubai, sparking an international terror alert.
The packages originated in Yemen, a key front in the fight against terrorism, and are believed to have contained the powerful explosive PETN.
Mr Cameron said: “We believe that the device was designed to go off on the aeroplane. We cannot be sure about the timing when that was mean to take place.
There is no early evidence it was designed to take place over British soil, but of course we cannot rule that out.”
Speaking at Chequers ahead of a meeting with German Chancellor Angela Merkel, he confirmed he had spoken to US president Barack Obama, adding: “I have also spoken to President Saleh of the Yemen making the point that we have to do even more to crack down and cut out the cancer of al Qaida in Yemen and the Arabian Peninsula.
“We have immediately banned packages coming to or through Britain from the Yemen and we will be looking extremely carefully at any further steps we have to take.
“In the end these terrorists think that our interconnectedness, our openness as modern countries is what makes us weak.
“They are wrong – it is a source of our strength, and we will use that strength, that determination, that power and that solidarity to defeat them.”
He said the package started in Yemen, landed in Germany and was then transported to Britain en route to America, adding: “It just shows how united and determined we have to be to defeat terrorism.”
Yemeni officials said they were hunting a number of suspects who are believed to have been using forged documents and ID cards and to be linked to al-Qaida in the Arabian Peninsula (AQAP).
Yemeni President Ali Abdullah Saleh said security forces surrounded a house where the woman was hiding after receiving intelligence from the US and United Arab Emirates.
The authorities were also investigating 24 other suspect packages, according to a security official, as well as questioning cargo workers at the airport and employees of the local shipping companies.
Speaking earlier, after a Cobra meeting of the UK Government’s emergency planning committee, Home Secretary Theresa May announced the device was “viable” and “could have exploded”.
She said: “The target of the device may have been an aircraft and, had it detonated, the aircraft could have been brought down.”
She said the threat level would remain at its current level of “severe”, which indicates a terrorist attack is “highly likely”.
Ms May said there was “no information to indicate another attack is imminent” but announced the stoppage of all unaccompanied air freight from Yemen moving into or through the UK.
The Metropolitan Police said initial tests indicated the device had the “potential to bring down an aircraft in flight if detonated”.
The Met’s Counter Terrorism Command is in close liaison with agencies both in the UK and abroad.
The suspicious package in Britain was on a UPS plane that flew in from Sana’a.
It was discovered in the early hours of yesterday following a tip-off from Saudi intelligence sources.
The device in Dubai was found onboard a FedEx flight from Yemen.
Both packages were addressed to synagogues in Chicago and were on Chicago-bound cargo planes.
Police in Dubai said the device there contained an electric circuit linked to a mobile phone chip as well as the compound lead azide, which can be used in detonators.
A spokesman said: “The parcel was prepared in a professional manner where a closed electrical circuit was connected to a mobile phone SIM card hidden inside the printer.
“This tactic carries the hallmarks of methods used previously by terrorist organisations such as al-Qaida.”
Direct cargo and passenger flights from Yemen to the UK were suspended in January this year after an attempt to blow up a Detroit-bound plane on Christmas day last year.
The so-called Underpants Bomber was also found with PETN and AQAP were behind the botched attempt.
The bomb finds will focus attention on the need for tight security checks and follows calls from airline bosses this week that existing procedures such as shoe and laptop checks should be scrapped.