The government’s emergency planning committee is to meet later to discuss the discovery of a suspected explosive package on a cargo flight from Yemen.
The device – a printer cartridge with wires protruding – was found on a plane at East Midlands Airport on Friday, and sparked an international terror alert.
The flight was bound for Chicago. Another device was found on a Chicago-bound cargo plane in Dubai.
The home secretary has said there was no indication that the UK was a target.
Home Secretary Theresa May will chair the emergency committee, known as Cobra.
She said air security for cargo planes was under review in the wake of the discovery, and direct flights from Yemen to the UK have been suspended.
Yemen is considered a source of a growing threat of extremist violence, with the Labour government earlier this year vowing to do more to combat it. The UK was working with the US to strengthen counter-terrorism there.
Mrs May said on Friday that it was unclear if the device was a “viable explosive device”, while the US described it as a “credible terrorist threat”.
Aviation expert Chris Yates said he had been told that the device also had a mobile phone attached. It could work as a remote detonation device, triggered by a phone call from anywhere in the world.
He said it was probably not possible to detonate while in the air, as mobile phones are short-range devices, and are out of range while at altitude.
“Cargo has always been seen as the Achilles heel of the aviation system. There are measures being taken for cargo, but those measures aren’t necessarily as robust as one might imagine, so it’s entirely possible that in some parts of the world a device such as this can be infiltrated into the cargo handling system and transported around the world on aircraft,” Mr Yates said.
Yemen has risen rapidly towards the top of the list of countries of concern for Western counter-terrorism officials in the past year. The group al-Qaeda in the Arabian Peninsula – which has found a sanctuary in Yemen’s ungoverned spaces – has shown increasing ambition and sophistication in its attempts to target the United States and others.
But while the origin of this plot seems clear, its exact form does not. The presence of explosives in the devices suggests this was no dry run or simply an attempt to cause panic through a hoax.
But forensic experts in the UK have been continuing to study the substances found in the parts for a printer to try to understand exactly what they were and how they were to be used. There appears to be a strong conviction these were parts for a bomb but whether they were complete and how they were to be detonated and against which target remains uncertain.
“It would seem from everything we’ve seen and heard in the last 12 hours that this was an intelligence-led operation, pointing the authorities to these devices. It’s by good fortune that this information came in.”
US President Barack Obama’s top counter-terrorism adviser John Brennan said the US was “remaining vigilant.”
The packages were destined for Jewish places of worship in Chicago, Mr Obama said.
“We also know that al-Qaeda in the Arabian Peninsula – a terrorist group based in Yemen – continues to plan attacks against our homeland, our citizens and our friends and allies,” Mr Obama said.
The alerts were:
Suspect package found at DubaiSuspect package found at East Midlands AirportThree cargo planes owned by the freight company UPS searched in Newark and PhiladelphiaUS fighter jets escorted Emirates flight 201 from Dubai into New York, with officials saying the action was being taken “out of an abundance of caution” because cargo from Yemen was on boardSuspect package from Yemen examined on a delivery lorry in New YorkBA flight from London to New York met by authorities amid reports of search of its cargo
Mr Obama stressed that new aviation security measures were being taken in light of the alert by the Department of Homeland Security, “including additional screening”.
US officials told Associated Press they believed the packages contained PETN (pentaerythritol tetranitrate) – the same powerful explosive used in the failed bombing of a US-bound airliner last Christmas Day. However, the officials said that full testing had not been completed.
US security services remain on a high level of vigilance in the wake of the attempted Times Square bombing in May and the alleged attempted Christmas Day attack.
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