Security jitters on eve of London Olympics

LONDON - Security jitters were being felt across the British capital on the eve of the London Olympics, with the biggest mall in Europe briefly evacuated Thursday and noticeable security changes in place at the Olympic Park.

Prime Minister David Cameron said, however, that he was confident that the games which Britain has worked to produce for years will be successful and safe.

"You can never provide a 100 percent guarantee but what I've seen, and what I've helped to coordinate is, I think, a fully joined-up effort that involves one of the best armed services anywhere in the world," Cameron told reporters Thursday. "I'm confident we can deliver on that, working with visiting delegations as well."

A fire alarm forced authorities briefly to clear the massive Westfield shopping mall beside the Olympic Park on Thursday afternoon. Hundreds of people flooded into the street, a day before the opening ceremony Friday night at nearby Olympic Stadium.

Police allowed shoppers to return after a few minutes. Westfield mall authorities said the alarm was triggered in a restaurant area.

Fears of terrorism have been at the center of preparations for the London Olympics, and authorities have twice been forced to deploy more troops in the last two weeks — first an extra 3,500, then another 1,200 — when security arrangements fell short.

Britain's Ministry of Defense also scrambled a Typhoon fighter jet Wednesday after an airplane lost contact with air traffic controllers. Communications were quickly restored and no further action was required.

Britain's terror threat level is at substantial, which means a terror attack is a strong possibility. It is a notch below severe, the level Britain has been at for most of time since the 2005 suicide bombings when 52 people were killed in morning rush-hour attacks on London trains and buses.

One British security official told The Associated Press there was no existing intelligence to indicate the threat level would change immediately. Several terror suspects have been arrested in the last month but none have been accused of plotting directly against the games. He spoke on condition of anonymity because he was not authorized to speak to the media.

Dozens of FBI agents and other U.S. personnel are helping their British counterparts secure the games.

At some Olympic Park security entrances on Thursday, there was a noticeable shift from having military personnel man the airport-like security machines to having civilian security guards. At one entrance, an AP reporter put his bags through security but the scanning machine that checks Olympic credentials was broken and the staff waved him through.

The G4S security firm, responsible for the bulk of Olympic security, said Thursday it was getting hundreds more workers each day and hoped to replace some military personnel. Company spokesman Adam Mynott said many new workers had passed the accreditation process or completed training. The hope, he said, is to numerically replace the extra military personnel.

The security firm was lambasted earlier this month by the government for failing to provide enough security personnel for the games.

Mynott said he would look into why the AP reporter's credential wasn't scanned but said the changes Thursday were routine station changes between civilian and military guards.

Cameron has promised to go after G4S if they don't fulfill their contract and to make sure the company helps pay for the cost of the additional military personnel. The firm expects to lose between 35 million and 50 million pounds ($54 million-$78 million) on its Olympic contract, equal to about 12 percent of its annual profit.

Still, both London residents and some visitors were on edge.

"It's sunny and I think a lot of people are really excited about the Olympics but there's also this sense of dread that something will happen," said Tally Winfield, a 25-year-old London bartender.

One American tourist said the extra security seemed a tad daunting.

"With the police all around and troops, you definitely feel like something could happen at any time," said Melissa Johnson, a 36-year-old tourist from Los Angeles. "I'm not sure if I feel safer or just more worried. Then again, at least there are fewer guns here, right?"