MOUNTAIN VIEW (CBS SF) — British intelligence authorities want access to encrypted messages sent via WhatsApp before the terrorist attack in London that killed 5 and injured at least 50 people.

According to authorities, Khalid Massood used the Mountain-View based app owned by Facebook in the moments before he drove a car into pedestrians on Westminster Bridge and fatally stabbed a police officer. The Islamic State has claimed responsibility for the attack, but is is unclear if there was any communications between IS and Massood.

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Ambulances, police vehicles and emergency services seen on Westminster Bridge on March 22, 2017 in London, England. (Photo by Carl Court/Getty Images)

British government officials are meeting with the Silicon Valley companies to demand their help in this latest push against encryption technology, which in the wrong hands, has stymied investigations into terrorist activities.

“We do want them to recognize that they have a responsibility to engage with government, to engage with law enforcement agencies when there is a terrorist situation,” said Amber Rudd, Britain’s Home Secretary in an interview with the BBC. “They cannot get away with saying we are in a different situation. They are not.”

“We need to make sure that organizations like WhatsApp, and there are plenty of others like that, don’t provide a secret place for terrorists to communicate with each other,” she said.

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Members of the public are treated by emergency services near Westminster Bridge and the Houses of Parliament. (Photo by Carl Court/Getty Images)

Tech companies have pushed back against such demands in the past, saying encryption is necessary to protect users’ privacy. End-to-end encryption prevents tech companies from eavesdropping on communications. Only the sender and receiver can read the message. With some apps, messages can be programmed to disappear from the users’ phone in a specified amount of time.

In 2015, Apple refused an FBI request to unlock the iPhone of of one of the killers in the San Bernadino terrorist attack. The agency was able to access the phone without Apple’s help.

Meantime, WhatsApp is working with British authorities in the wake of the attack.

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“We are horrified by the attack carried out in London and are cooperating with law enforcement as they continue their investigations,” said spokesperson Lena Pietsch in a statement.