Cargo bomb carried on passenger plane

Air travellers face no let up in stringent security checks after it emerged one of the cargo plane bombs was transported on passenger aircraft before being found.

There are also fears that more explosive devices may still be at large, raising more questions about the safety of freight transportation as well as the difficulty of detecting explosive material.

Qatar Airlines confirmed the parcel bomb discovered in Dubai was transported on two separate passenger jets before being found by security staff.

Along with the other ink cartridge bomb found at Britain's East Midlands Airport on Friday, it is understood to have contained the powerful explosive material PETN.

Both devices originated in Yemen and were found only after a tip-off from Saudi intelligence.

The alert followed calls last week from airline bosses that existing security procedures such as shoe and laptop checks should be scrapped.

A huge anti-terror probe was focusing today on Saudi-born bomb-maker Ibrahim Hassan al-Asiri as the prime suspect for making the bombs.

He is also believed to have been responsible for making the device involved in the failed Christmas Day bomb plot over Detroit last year.

Yemeni police yesterday released student Hanan al-Samawi, 22, who was arrested on suspicion of sending the packages. A shipping agent said she was not the same person who signed the shipping documents.

US deputy national security adviser John Brennan aired fears about the extent of the latest plot, saying: “We’re trying to get a better handle on what else may be out there.

“We’re trying to understand better what we may be facing.”

He added that “it would be very imprudent ... to presume that there are no others (packages) out there.”

Cobra, the UK government’s emergency planning committee, will meet again today to discuss the plot and air transport implications.

Yemen, the ancestral home of Osama bin Laden, is a key front in the fight on terrorism.