British police on Friday said they had foiled an active terrorism plot after they shot a woman during a raid conducted at a house in north London, Reuters reported. The woman’s condition is said to be serious, the police said adding the she had not been arrested yet.

A 16-year-old boy, a man and woman were arrested from the scene. A 43-year-old woman was also arrested from Kent during investigations, reported BBC. Two more people, a man and a woman, were arrested hours later when they returned to the raided house, the police said.

Deputy assistant commissioner of Metropolitan Police, Neil Basu, said the house that was raided had been under observation for some time as part of a current counter-terrorism investigation. “An armed entry was necessary due to the nature of the intelligence that we were dealing with, and involved armed officers firing CS [tear gas] into the address,” Basu said.

The incident came a day after the police had arrested a man for allegedly carrying large knives in a bag near the Houses of Parliament in London. However, the police said the incidents were not related.

Talking about both the arrests, Basu said, “I believe that we have contained the threats that they posed.” Searches were being conducted at three places in London as part of the investigation, the officer added.

Security has been heightened in London since March 22, when a man had mowed people down with his vehicle on the Westminster bridge while heading to the Parliament building. At least 40 others were injured in the incident. The assailant was later identified as Khalid Masood, a 52-year-old Central England resident.