A large kitchen knife and brick used in the fatal attack on MQM leader Imran Farooq, has been recovered by the Scotland Yard, at the spot where he was killed last month.
The five and a half inch blade and house brick were found in Green Lane, where the 50-year-old was assaulted on September 16, a Scotland Yard spokesman said.
Officers are trying to trace two Asian men in connection with Farooq's murder.
"Detectives have recovered a 5.5-inch (14cm) bladed kitchen knife and a house brick which were used in the attack on Dr Farooq in Edgware two weeks ago," the spokesman said.
The officials have as yet made no arrests, but they have not ruled out a political motive behind the killing.
Farooq was a prominent member of Pakistan's Muttahida Quami Movement, one the largest parties of the country.
Farooq had been living in exile in London after fleeing the country 11 years ago.
He was wanted in Pakistan over scores of charges, including torture and murder related to MQM's activities. However, he had maintained that the accusations were politically motivated.
His murder sparked violence in Karachi where buildings and vehicles were set alight, despite a public appeal for 10 days of peaceful mourning.
The MQM is a partner in the ruling coalition led by President Asif Ali Zardari's Pakistan People's Party in the southern province of Sindh, of which Karachi is the capital.
A police spokesman said: "A number of witnesses have already contacted police, but officers believe there are other people who may hold vital information about the incident and they continue to urge them to come forward".
"Officers from the Specialist Operations Counter Terrorism Command want to speak to anyone who saw the attack or was in the area at the time," he said.
The Observer on Sunday reported that Farooq may have been about to leave the MQM and join a new party being launched by former president Pervez Musharraf, who also lives in London.