Police carried out a controlled explosion of a package discovered near Parliament this evening.
The package was declared safe and cordons in the area were lifted.
The package was found on Birdcage Walk near Downing Street.
Four people died in yesterday's attack, after a car was driven along the pavement on Westminster Bridge and a policeman was stabbed outside the Houses of Parliament. Masood was shot dead at the scene.
In total, eight people have been arrested in connection with the incident.
The man police believe to be responsible for the terrorist attack in Westminster yesterday, Wednesday, 22 March, has now been formally identified as Khalid Masood.
According to a statement from the Metropolitan Police, Masood, aged 52, was born in Kent and detectives believe he was most recently living in the West Midlands. Masood was also known by a number of aliases.
The Prime Minister told the House of Commons this morning that the attacker was British-born and "known to MI5".