Passenger with electrical circuits in shoes held at airport

Officials were investigating what the components could be used for and why they were concealed. Similar materials can be used in the construction of bombs.

The man, Faiz Mohammad, was arrested at Karachi's Jinnah International Airport on Sunday night, said Munir Ahmed, a spokesman for the airport security force. The materials were detected by a scanner.

Mr Ahmed said each shoe contained a small circuit connected to two AAA batteries.

Mohammad, a building constructor who was heading for Muscat in Oman, told investigators he bought the shoes from a market in Karachi and had no idea there were circuits hidden inside the soles.

"It is premature to say what was he up to. We are looking into the

matter thoroughly," police official Sohail Faiz said.

In 2001, British extremist Richard Reid, left, was arrested after he tried to detonate explosives hidden in his shoes on a transatlantic flight.

Pakistan's security efforts have come under scrutiny since an alleged Pakistani-trained extremist was accused of a failed car bombing in

Times Square last week. Top US officials have said the Pakistani Taliban wasbehind the plot.

Karachi, Pakistan's largest city, was targeted by authorities in the investigation into the Times Square bombing attempt. Four people with alleged links to a militant group affiliated with al-Qaida were detained there.