San Francisco — The San Francisco International Airport was evacuated Wednesday after security guards detected explosives residue on the shoes of a man who then disappeared into the crowd.
Thousands of passengers waited outside while 28 gates were closed for about two hours and the United Airlines terminal was searched. The man was not found. The terminal was reopened mid-morning and passengers were rescreened, said airport spokesman Ron Wilson.
"This individual probably has no idea he was the cause of so much disruption this morning," Wilson said. "He is not a mad bomber or a terrorist."
The explosive material could be anything from fireworks residue to nitroglycerin tablets, airport officials said. The substance "is similar to a plastic explosive, but has the same signature in many respects as common fertilizer," Wilson said.
He said the man may have simply walked across a fertilized lawn earlier Wednesday.
The residue was detected after a gauze-like material was wiped across the man's brown loafers, then put through a machine. It triggered an alarm during the random screening. While a guard checked with his supervisor, the man put on his shoes and walked away.
"When they went to stop him, he didn't stop," said Mike McCarron, another airport spokesman.
Airport officials say the man may have left on one of the two planes that departed after the alarm sounded.
Passengers were forced to stand in the road in front of the terminal building on an unusually cold San Francisco morning, with temperatures in the 30s.
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