The Islamic State group claimed one of its "soldiers" carried out the attack, the worst in Britain since the July 2005 bombings that left 52 people dead.
More than 50 people of a dozen nationalities were injured, 31 of whom required hospital treatment.
Investigators do not now see a direct ISIS hand in this week's attack in London, a British counterterrorism official told CNN on Saturday.
In the recent development, two more significant arrests have been made by the London police on Friday in connection with the attack.
"We remain keen to hear from anyone who knew Khalid Masood well, understands who his associates were and can provide with information about places he has recently visited", Rowley said.
"Our determination is to find out if either he acted totally alone, inspired by perhaps terrorist propaganda, or if others had encouraged, supported or directed him", said Rowley.
The picture shows bearded terrorist Khalid Masood, formally known as Adrian Ajao.
Masood was staying at a hotel in Brighton since Tuesday and, according to the hotel's manager, he was "laughing and joking" in Brighton the night before making his fatal journey to London. Two people are in critical condition, and another has life-threatening injuries.
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Nunes said no, but added: "We're beginning to figure out who's actually serious about the investigation". Comey comes in, it's a little tough for us to do depositions and interviews", Nunes said.
Little else is known about the 52-year-old, who plowed an SUV through pedestrians on Westminster Bridge before stabbing a police officer to death outside the Parliament in an attack later claimed by ISIS. Authorities on Thursday identified a 52-year-old Briton as the man who mowed down pedestrians and stabbed a policeman to death outside Parliament in London, saying he had a long criminal record and once was investigated for extremism - but was not now on a terrorism watch list.
Nine people are now in custody after a woman was released on bail.
A 35-year-old man and a 32-year-old woman were arrested at separate locations in Manchester on Friday.
Detectives from the Metropolitan Police's Counter Terrorism Command confirmed after detailed probe that the attack started at 14:40:08 (local time) on Wednesday when the vehicle that Masood was driving over Westminster Bridge first mounted the northbound pavement.
Detectives confirmed the attack was over within 82 seconds.
"Our working assumption is that he was inspired by global terrorism", said Britain's most senior counterterrorism police officer, Mark Rowley, adding: "Islamist-related terrorism is our assumption".
The English teacher had a string of aliases and was born in South East London under the name Adrian Elms.
"An act of terrorism tried to silence our democracy", May told parliament.