According to US media reports, the United States Federal Bureau of investigation (FBI) and the National Security Agency recently issued a joint announcement warning that terrorists are still trying to use the "modified shoes to hide explosive devices."

The European security department found a pair of shoes on a bus last month, which concealed bomb detonators tactfully inside the shoes of the naughty shoes.

Intelligence officials say no one is wearing these shoes.

The documents said the shoes were used for cross border smuggling of fire detonators for terrorist attacks.

"Terrorists have been interested in explosive devices, and they are trying to find the best way to escape explosives," said Kurt Azee, a counterterrorism analyst at Columbia news program.

Terrorists used to use shoes as a way of hiding explosives.

Reed, a member of the Al Qaeda group, tried to blow up a US airliner with a bomb in the shoe root for 3 months before the "911" terrorist attack.

All the airports in the United States now conduct X - ray scanning of all passengers' shoes and handbags.

However, experts are still worried about terrorist groups carrying unassembled bombs through security checks.

Wright, the head of the bomb squad of the former New York police force, said: "a terrorist will carry part A, and another terrorist will carry part B. They will rendezvous the bomb after passing the security check."

Officials say there is no concrete information that terrorists are preparing to launch a new attack on the United States.

But the risk of terrorist attacks is still high.

A notice issued by the Federal Bureau of investigation and the Department of Homeland Security warned law enforcement officials not to take lightly the daily items such as shoes.