Armed police have carried out an overnight raid on a Birmingham property, which was reportedly linked to the attack in Westminster on Wednesday.
Counter-terror detectives are continuing to search for clues about about how an armed attacker, believed to have "inspired by international terrorism", brought death and destruction to the streets of London.
Five people were killed in the "sick and depraved" terror attack, including a police officer who was stabbed and his assailant, while dozens more were injured.
Armed police launched a late-night raid on a second-floor flat above a row of shops on Hagley Road in Birmingham. Witnesses have said three people were taken away by police.
Sky News cited unnamed sources as saying the action was linked to the attack in London.
BBC Newsnight had earlier reported there was a suggestion the car used in the attack was hired from an address in Birmingham. However, this has not been confirmed.
Mark Rowley, Scotland Yard's top anti-terror officer, confirmed that 40 people were injured after the attacker - armed with two large knives - mowed down pedestrians with his car on Westminster Bridge then rushed at the gates in front of the Houses of Parliament, stabbing a plain-clothes policeman before he was shot by armed officers.