San Francisco airport evacuated as explosive found on passenger's shoe

A terminal at San Francisco airport was evacuated yesterday after a passenger, described as a white male in his 40s, tested positive for explosive traces on his shoes but then promptly vanished from the security checkpoint.

Police launched a search for the man but failed to locate him, while hundreds of travellers were herded outside the United Airlines terminal building at the height of the morning rush.

Airport officials said they were not sure whether he deliberately ran away or whether he simply walked off without realising that security officials had not finished with him. "When they came back to ask him more questions, he was gone," an airport spokesman, Mike McCarron, said. "He was lost in the crowd. He just walked away."

The man was selected for a random security search – a procedure introduced in response to 11 September. Shoe tests have become a standard part of such searches since the arrest of Richard Reid, the British man restrained on board a Paris to Miami flight after he lit a match and apparently attempted to set off explosives hidden in his high-ankle sports shoes.

Shortly before 7am local time, the security guards at San Francisco wiped a piece of gauze over the man's shoes and then entered it into a machine. It came back with a positive reading.

Mr McCarron said the identified substance could have been anything from fireworks residue to nitroglycerin.

It was not immediately clear whether airport officials knew the man's name or whether his face had been captured on a video surveillance camera. As many as 3,000 people were told to leave the terminal, San Francisco's busiest, and were left milling about on the pavement outside for up to three hours.

Security officials then checked the building for unauthorised people and suspicious packages, then reopened the terminal for normal business.

"We've searched the terminal. It's safe and secure," another airport spokesman, Ron Wilson, said. "It's unfortunate that one individual can cause this madness." The stoppage played havoc with air connections across the United States.

Similar incidents have occurred sporadically at various American airports in recent weeks. A concourse at Miami international airport was evacuated on Monday night after a man told security personnel that they had failed to spot a gun in his bag. He, too, walked off and could not be found.