Photos of the London Olympic Park, Stadium and Orbit Tower.
LONDON (AP) -- Security jitters are being felt in the British capital on the eve of the official opening of the London Olympics.
A big shopping mall next to Olympic Park was briefly evacuated today after a fire alarm went off. It was triggered in a restaurant area.
Yesterday, British defense officials scrambled a Typhoon fighter jet after a plane lost contact with air traffic controllers.
Fears of terrorism have been at the center of preparations for the Olympics. A London bartender says "a lot of people are really excited about the Olympics" -- but that there's also a "sense of dread that something will happen."
Britain's terror threat level is at substantial, which means a terror attack is a strong possibility. But that's a notch below severe.
One British security official says there's no existing intelligence to indicate the threat level would change immediately.
Prime Minister David Cameron says he's confident the games will be successful and safe.
Dozens of FBI agents and other American personnel are helping their British counterparts secure the games.