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. Last Updated: 07/27/2016

British Police Foil Terrorist Plot at Heathrow

LONDON -- British authorities said Thursday that they had thwarted a terrorist plot to simultaneously blow up several aircraft flying to the United States using explosives smuggled in hand luggage, averting what police described as "mass murder on an unimaginable scale."

Police arrested 21 people and said they were confident they had captured the main suspects in the alleged plot.

Officials raised security to its highest level -- suggesting a terrorist attack might be imminent -- and banned carry-on luggage on all trans-Atlantic flights. Huge crowds formed at security barriers as officials searching for explosives barred nearly every form of liquid outside of baby formula.

"This was to be a simultaneous attack on multiple targets, targeting U.S.-bound aircraft," a police official said, speaking on condition of anonymity because of the sensitivity of the case.

The extreme measures at one of the world's largest aviation hubs sent ripples throughout the world. Heathrow airport was closed to most flights from Europe.

Deputy Police Commissioner Paul Stephenson said Thursday that police were confident they had disrupted the plot.

Police arrested 21 people in London, its suburbs and in Birmingham, central England. Searches continued in a number of locations.

The suspects were "homegrown," though it was not immediately clear if they were all British citizens, the police official said, adding that police were working with the South Asian community.

Prime Minister Tony Blair, vacationing in the Caribbean, briefed U.S. President George W. Bush on the situation, Blair's office said.

The months-long investigation into the suspected terrorist plot had global dimensions and involved unprecedented surveillance, police anti-terrorist chief Peter Clarke said.

Britain's Home Secretary John Reid said Britain's threat status would remain at the highest level for the time being "as a precautionary measure."

"Whilst the police are confident that the main players have been accounted for, neither they nor the government are in any way complacent," Reid said. "This is an ongoing, complex operation."

Passengers faced delays as tighter security was hastily enforced at the country's airports and additional measures were put in place for all flights. British Airways canceled all flights Thursday between Heathrow airport and points in Britain, Europe and Libya.

Laptop computers, mobile phones, iPods and remote controls were among the items banned from being carried on board.

Liquids, such as hair care products, were also barred. U.S. Homeland Security Secretary Michael Chertoff raised the possibility that authorities were searching for a liquid explosive.

"Due to the nature of the threat revealed by this investigation, we are prohibiting any liquids, including beverages, hair gels and lotions, from being carried on the airplane," Chertoff said.

Authorities in the United States imposed bans on carry-on aerosols and most liquids on planes serving East Asia in 1995, after a plot was uncovered to use liquid bombs to bring down U.S. aircraft over the Pacific.

The plot was allegedly developed by Ramzi Yousef, thought to be the mastermind of the 1993 World Trade Center bombing, and was discovered after police raided his apartment in Manila in 1995. Police believed Yousef was in the Philippines to try to assassinate Pope John Paul II during a visit to Manila that year.

Huge lines formed at ticket counters and behind security barriers at Heathrow and other airports in Britain. Ed Lappen, 55, a businessman from Boston traveling with his wife and daughter to Russia, found himself temporarily stranded.

"We're safe, we're OK," he said at Heathrow. "Now my daughter is going to get a shopping trip in London."