A US-bound package intercepted on a plane in Dubai contained explosives and bore the hallmarks of al-Qaida, Dubai police said today as international security services continued to investigate the terrorist threat.
The announcement came after security services in the UK and Dubai yesterday thwarted an alleged attempt to send explosive material hidden in printer ink cartridges by air from Yemen to strike targets in the US.
The device found on board a cargo plane in Dubai contained pentaerythritol trinitrate (PETN), the same explosive used in a failed plot to bomb a plane to Detroit in December 2009, police said in a statement.
"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."
Intelligence agencies believe the Dubai package and another found at East Midlands airport are linked to a Yemen-based group called al-Qaida in the Arabian Peninsula.
The US homeland security secretary, Janet Napolitano, supported the Dubai authorities' assessment in an interview today on ABC News.
"I think we would agree ... that it does contain all the hallmarks of al-Qaida and in particular al-Qaida AP," she said.
The packages – described by Barack Obama as "a credible terrorist threat" – were addressed to Jewish synagogues in the Chicago area. One UK security source said that despite the president's announcement, the aim was probably to cause panic rather than bomb any particular target.
The Dubai device contained lead azide, an explosive compound which can be used in detonators. The police said they were tipped off by a call from abroad that warned of the possibility of an explosive device hidden in postal packages onboard the FedEx flight from Yemen.
Napolitano said checks were being done to establish whether other packages had been sent before the two that were intercepted.
"We're doing some reverse engineering, as it were, to identify other packages from Yemen," she told NBC News.
She said it was too early to say whether the packages were meant to blow up while airborne or when they reached their destinations.
Counterterrorism sources told the Guardian the device discovered in the UK was found after specific intelligence led to a decision to do extra searches of cargo on the plane.
Last night John Brennan, assistant to the US president and deputy national security adviser for homeland security and counterterrorism, said Saudi Arabia had provided vital information.
The British home secretary, Theresa May, confirmed that the package found at East Midlands airport did contain explosive material, but said it was not yet clear whether it was a "viable explosive device".
May, who spoke with Napolitano yesterday, said: "The package which originated in Yemen was removed for forensic examination by UK experts. That examination continues.
"We are reviewing the security measures for air freight from Yemen and are in discussion with industry contacts."
Cobra, the government's emergency planning committee, was meeting today to discuss the situation but David Cameron, who is at his Chequers country residence, was not due to take part. Downing Street said the prime minister had spoken to May last night and was being kept up-to-date with the situation.
The plane that landed in the UK was operated by the parcel company UPS (United Parcel Service). It had taken off from Yemen's capital Sana'a, and was due to fly to two locations in the US. At 3.30am yesterday, it made a routine stop at the UK's largest freight airport where it was subjected to extra searches.
A source with close knowledge of the events said a large box was found by employees carrying out screening checks in the UPS facility. Initial checks were inconclusive and the UPS flight was allowed to fly on to the US without the box on board. But the discovery of a freight bomb in Dubai prompted a further check which revealed that a toner cartridge for a Hewlett Packard printer contained a hidden suspect device. It was wired with a mobile phone, most likely to act as a timer to detonate the device.
The device was split in two and sent for scientific investigation. Minutes after the find, Obama was told in Washington of the discovery, amid concerns that some sort of terrorist action emanating from Yemen was feared.
Police put up a security cordon around the airport yesterday morning, which was finally lifted at 5.35pm. Other UK airports were not affected by the find.
Obama, speaking in Washington days before the midterm elections, said Yemen's president had pledged to co-operate in the investigation. He effectively named the Islamist group al-Qaida in the Arabian Peninsula as the chief suspects.
"I've also directed that we spare no effort in investigating the origins of these suspicious packages and their connection to any additional terrorist plotting. Although we are still pursuing all the facts, we do know that the packages originated in Yemen. We also know that al-Qaida in the Arabian Peninsula, a terrorist group based in Yemen, continues to plan attacks against our homeland, our citizens, and our friends and allies."
Concerns about other devices prompted major security alerts across US cities. Jewish groups in Chicago and New York were warned that they may be a target for dangerous packages. Fed Ex said it was suspending all deliveries from Yemen.
UPS jets in Philadelphia and Newark, New Jersey, were moved away from terminal buildings and two fighter jets escorted an airliner travelling into New York from Dubai.
The terror alert followed calls this week from British airline bosses that existing security procedures such as shoe and laptop checks should be scrapped.
The former home secretary Lord Reid told BBC News today: "The important thing is to remember that even when there are no incidents like this, there is still a huge and continuing threat from terrorism, not just from al-Qaida but its affiliates and in some cases from brand new groupings.
"We've got to get away from this idea that if we go a period of time without an incident like this that somehow we can reduce vigilance and reduce security at airports."
Yemen has been of increasing concern to western counterterrorism officials, who suspect its use as a base for al-Qaida-inspired terrorists. American officials said intelligence agencies had, over recent months, tracked three other packages out of Yemen for delivery to the US that appeared to be trial runs for the smuggling of a bomb on board a cargo plane. They said the grounding of planes from the US and UK to Dubai for further searches was partly based on that intelligence.
Earlier this year, the US and Britain temporarily closed embassies in the Yemeni capital over fears of a terrorist attack.
Gordon Brown banned direct passenger flights from Yemen to the UK in January. The US department for homeland security said it had taken a "number of steps" to enhance aviation security last night.
